|
|
The cable interface in the Cisco uBR7200 series router supports downstream and upstream signals, and serves as the cable TV radio frequency (RF) interface. The downstream signal is output as an intermediate-frequency (IF) signal suitable for use with an external upconverter. Your cable plant, combined with your planned and installed subscriber base, service offering, and external network connections, determines the combination of cable interfaces, network uplink line cards, and other components that you should use.
The Cisco IOS software command-line interface (CLI) can be used to configure the Cisco cable interface line card for correct operation on the hybrid fiber-coaxial (HFC) cable network. This chapter describes the several required and optional tasks that configure the Cisco cable interface line card.
 |
Note For additional information about CMs on the HFC network, refer to "Managing Cable Modems on the Hybrid Fiber-Coaxial Network." |
Perform the tasks in the following sections for required and optional cable interface configurations:
| Section | Description |
|---|---|
Provides instructions for performing required downstream configuration tasks. | |
Provides instructions for performing required upstream configuration tasks. | |
"Configuring Optional Cable Modem Interface Features" section | Provides instructions for performing several optional CM interface configurations. |
These configurations are required. The first step in configuring the Cisco CM interface is to configure the downstream cable interface. Configuring the downstream cable interface consists of the following procedures:
| Task | Description |
|---|---|
"Activating Downstream Cable Address Resolution Protocol Requests" section | Provides instructions to activate ARP requests on the cable interface so that the Cisco uBR7200 series CMTS can perform IP address resolution on the downstream path. |
Provides instructions to activate and verify a downstream port on a cable interface card for digital data transmissions over the HFC network. | |
Provides instructions to assign and verify a numeric channel ID to the downstream port on the Cisco cable interface line card. | |
"Configuring Downstream Rate Limiting and Traffic Shaping" section | Provides instructions for using the cable downstream rate-limit token-bucket command, which configures rate limiting and traffic shaping on the downstream channel. |
Provides instructions to specify an IP address of a Dynamic Host Configuration Protocol (DHCP) server where User Datagram Protocol (UDP) broadcast packets will be sent. | |
Provides instructions to set the downstream interleave depth in milliseconds for the downstream port on the Cisco cable interface line card. | |
Provides instructions to define the speed in symbols per second at which data travels downstream to the subscriber's CM. | |
Provides instructions to set and verify the downstream MPEG framing format, which must be compatible with DOCSIS specifications and your local cable plant operations. | |
Provides instructions to use the token bucket policing algorithm with traffic shaping options or the weighted discard algorithm to buffer, shape, or discard packets that exceed a set bandwidth. |
|
Note In most applications, default values for the commands used in these configuration steps are adequate to configure the Cisco uBR7200 series router. You do not need to specify individual parameters unless you want to deviate from system defaults. |
For information on other configuration options, refer to the Cisco Broadband Cable Command Reference Guide on Cisco.com.
This configuration is required. Address Resolution Protocol (ARP) is an Internet protocol used to map IP addresses to MAC addresses on computers and other equipment installed in a network. You must activate ARP requests on the cable interface so that the Cisco uBR7200 series CMTS can perform IP address resolution on the downstream path.
|
Note The default values for the commands used in this configuration step are adequate in most cases to configure the Cisco uBR7200 series CMTS. |
To activate ARP requests, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)# cable arp | Enable ARP. This is the default. |
To verify that cable ARP is activated, enter the more system:running-config command and look for the cable interface configuration information. If ARP is activated, it does not appear in this output. If ARP is deactivated, it appears in the output as no cable arp.
Router# more system:running-config
Building configuration...
Current configuration:
!
interface cable5/0
ip address 1.1.1.1 255.255.255.0
no keepalive
no cable arp
cable downstream annex B
cable downstream modulation 64qam
cable downstream interleave-depth 32
cable downstream symbol-rate 5056941
cable upstream 0 frequency 15008000
no cable upstream 0 shutdown
 |
Tip If you are having difficulty with verification, verify that you entered the correct port and cable interface line card slot number when you activated ARP and when you entered the show interface cable command. |
To activate a downstream port on a Cisco uBR7200 series cable interface card for digital data transmissions over the HFC network, complete the steps in the following table.
| Command | Purpose | |
|---|---|---|
Step 1 | | Enters enable (privileged EXEC) mode. Enter the password. You have entered privileged EXEC mode when the prompt displays the pound symbol |
Step 2 |
| Enters global configuration mode. You have entered global configuration mode when the This command can be abbreviated to config t or conf t. |
Step 3 |
| Enters cable interface configuration mode. In this example, the interface is downstream port 0 on the cable interface card installed in slot 1 of the Cisco uBR7200 series CMTS. |
Step 4 | | Default. Activates downstream digital data from the Cisco uBR7200 series router. |
Step 5 | | Places the downstream port in the "admin up" state. |
Step 6 | | Returns to privileged EXEC mode. |
To determine if the downstream carrier is active (up), enter the show controllers cable command for the downstream port that you just configured. For National Television Standards Committee (NTSC) 6 MHz operations, see the following example:
Router# show controllers cable5/0 downstream
Cable5/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
The Cisco uBR7200 series router supports an integrated upconverter that outputs a DOCSIS RF signal on the DS0 RF downstream port. To enable the integrated upconverter, you must do the following:
|
Note The cable downstream frequency command has no effect on external upconverters. If you are using an external upconverter, this command is informational only and you must configure the external upconverter separately, using its own command procedures. |
To configure the integrated upconverter, use the following commands in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config)# interface cable 1/0 | Enter interface configuration mode for the cable interface on the Cisco uBR7200 series router. |
Router(config-if)# cable downstream frequency down-freq-hz | Enter the fixed center frequency for your downstream RF carrier in Hz. Allowable DOCSIS center frequencies are 91,000,000 to 857,000,000 Hz (the default is 500,000,000 Hz). |
Router(config-if)# no cable downstream rf-shutdown | Enable the integrated upconverter. |
Router(config-if)# no shutdown | Enable the cable interface. |
To verify the configuration for the integrated upconverter, enter the show controllers cable downstream command. The following is a typical display with a correctly configured center frequency:
Router# show controllers cable1/0 downstream Cable1/0 Downstream is up Frequency=525000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4 Downstream channel ID: 0
Then enter the show controllers cable command, which also displays the center frequency, along with the power levels and whether the integrated upconverter is enabled. The following is a typical display when these values have been correctly configured:
Router# show controllers cable1/0 Interface Cable1/0 Hardware is IMC11 BCM3210 revision=0x56B2 Cable1/0 Upconverter is Enabled Output is Enabled Model: 74-2094-01 Serial Number: 0WAV04480010 CLEI Code: CLEI# HW Rev: PC2D0107 SW Rev: 007, NVRAM Rev: 006 ECI number 123456 Downstream Frequency 525.0000 MHz IF Power 0.3 dBmv RF Power 51.0 dBmv ...
If the center frequency has not been configured, the frequency is shown as "not set" as shown in the following example:
Router# show controllers cable1/0 downstream Cable1/0 Downstream is up Frequency is not set. Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4 Downstream channel ID: 0
If you are having trouble, make sure the cable connections are not loose or disconnected, and that you have calculated and entered the center frequency for your router accurately.
Router(config-if)# cable downstream channel-id id
|
Note The cable downstream channel-id command must be used with the following command: cable downstream frequency 54000000-1000000000 broadcast frequency - h
|
These commands are used in instances where you want to send multiple downstream frequencies to a single region that contains CMs that can connect only to upstream ports on the same cable interface line card. You must configure unique channel IDs for each downstream that any CM is capable of receiving. The downstream frequency setting must match the setting on the upconverter.
 |
Caution After defining unique downstream IDs, test the CMs for correct operation. Cisco recommends that when using this feature, you re-test each subsequent software release of CM code to verify correct operation and to ensure reasonable acquisition time for new installations. Failure to use these commands in conjunction or to test the involved CMs can result in customer service outages of indefinite duration. |
To verify the downstream channel ID, enter the show controllers cable command for the downstream port you have just configured. See the following example:
Router# show controllers cable5/0 downstream
Cable5/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 1
To configure downstream traffic shaping, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)#[no] cable downstream rate-limit token-bucket [shaping] weighted-discard [expwt <n>] | Enables or disables rate limiting and traffic shaping on the downstream of a cable interface. |
|
Note Using Cisco IOS Release 12.0(5)T1 or higher, the software adds downstream calendar queuing routines and grant shaping application of the calendar queues. |
Details for key command usage are provided below:
Specify an IP address of a Dynamic Host Configuration Protocol (DHCP) server where User Datagram Protocol (UDP) broadcast packets will be sent. You can specify a DHCP server for UDP broadcast packets from cable interfaces, and a DHCP server for UDP broadcast packets from hosts. To set a downstream helper address, use the following commands in cable interface configuration mode.
| Command | Purpose | |
|---|---|---|
Step 1 |
| Set the downstream helper address to the DHCP server at IP address 10.x.x.x for UDP broadcast packets from cable modems. Note Use the IP address of the DHCP server. Both 10.x.x.x and 172.56.x.x are private ranges. |
Step 2 |
| Set the downstream helper address to the DHCP server at IP address 172.56.x.x for UDP broadcast packets from hosts. |
To verify the downstream helper address setting, enter the show running-config command and look for cable helper-address in the cable interface configuration information:
Router# show running-config Building configuration... Current configuration: ! interface cable5/0 ip address 10.254.254.254 255.0.0.0 no ip directed-broadcast cable helper-address 192.168.1.1 no keepalive
Perform these steps if you are having difficulty with verification:
Step 2 Check the cables, RF levels, and upstream frequencies, and enter a no shut command if the cable interfaces find a downstream signal, but not an upstream signal.
Step 3 Check the provisioning servers.
Step 4 Check DHCP options and the IP address of the Time-of-Day (ToD) server:
Set the interleave depth for the downstream port on the Cisco cable interface line card. A higher interleave depth provides more protection from bursts of noise on the HFC network; however, it increases downstream latency.
|
Note The valid values are 8, 16, 32 (default), 64, and 128. |
Router(config-if)# cable downstream interleave-depth {8|16|32 |64|128}
To verify the downstream interleave depth setting, enter the show controllers cable command for the downstream port you have just configured:
Router# show controllers cable5/0 downstream
Cable5/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that the downstream carrier is active, using the cable downstream if-output command.
|
Note Setting a downstream modulation rate of QAM-256 requires approximately a 6 dB higher signal-to-noise ratio (SNR) than QAM-64 at the subscriber's cable interface. If your network is marginal or unreliable at QAM-256, use the QAM-64 format instead. Also, consider the significance of your data. |
To set the downstream modulation, use the following command in cable interface configuration mode. The standard DOCSIS modulation rate (and the Cisco default) is QAM-64.
Router(config-if)# cable downstream modulation 64qam
To verify the downstream modulation setting, enter the show controllers cable command for the downstream port you have just configured. See the following example:
Router# show controllers cable5/0 downstream
Cable5/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers
Step 5 Verify that the downstream carrier is active, using the cable downstream if-output command
Step 6 Verify that you have selected the default if you are not certain about the modulation rate needed.
The MPEG framing format must be compatible with DOCSIS specifications at http://www.cablemodem.com/specifications.html and your local cable plant operations.
|
Tip Annex B is the DOCSIS MPEG framing format standard for North America. |
|
Note Annex B framing format is automatically set when configuring Cisco cable interface line cards. The cable interface line card's downstream ports and the connected CMs on the network must be set to the same MPEG framing format and must support DOCSIS operations as appropriate. |
Router(config-if)# cable downstream annex {B}
To verify the downstream MPEG framing format setting, enter the show controllers cable command for the downstream port you have just configured. See the following example:
Router# show controllers cable5/0 downstream
Cable5/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 0
Downstream traffic shaping enables you to use the token bucket policing algorithm with traffic shaping options or the weighted discard algorithm to buffer, shape, or discard packets that exceed a set bandwidth. Downstream traffic shaping is disabled by default.
| Command | Purpose | |
|---|---|---|
Step 1 | | Enables traffic shaping on the downstream port using the token bucket policing algorithm. With this command, the Cisco uBR7200 series router automatically drops packets that are in violation of the allowable bandwidth. |
Step 2 | | Enables traffic shaping on the downstream port using the weighted discard algorithm and assigns a weight for the exponential moving average of the loss rate. Acceptable values are 1 to 4. |
Step 3 | Router(config-if)# | Exits back to EXEC mode so that you can verify the steps. |
To determine if downstream traffic shaping is configured and activated, enter the show running-config command and look for the cable interface configuration information. If downstream traffic shaping is configured and enabled, a traffic shaping entry appears in the output. If downstream traffic shaping is disabled, no traffic shaping entry appears.
Router# show running-config Building configuration... Current configuration: ! interface cable5/0 ip address 10.254.254.254 255.0.0.0 no ip directed-broadcast cable helper-address 192.168.1.1 no keepalive cable downstream annex B cable downstream modulation 64qam
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected the default if you are not certain about the modulation rate needed.
Step 6 Verify that the downstream carrier is active using the cable downstream if-output command.
These configurations are required. Upstream cable interface commands configure the frequency and input power level of the upstream signal, in addition to error detection and correction of the upstream signal. The configuration of the upstream cable interface depends on the characteristics of your cable plant.
Perform the following tasks in this section to configure the upstream cable interface.
|
Note For some of these tasks, default values are adequate to configure the device.
|
Upstream admission control tallies up the total amount of guaranteed minimum upstream throughput reserved by CMs on an upstream interface. Once the total exceeds an allowable level, no more CMs requiring a guaranteed minimum upstream rate are allowed online on that upstream port.
Cisco CMTS upstream admission control is turned off by default and must be activated. To set the upstream admission control as a percentage of the upstream channel capacity, use the following command in cable interface configuration mode. The admission control is set as a percentage of the specified upstream channel capacity. The acceptable range is from 10 to 1000 percent.
Router(config-if)# cable upstream usport admission-control percentage
For example:
7246VXR(config-if)#cable upstream 0 admission-control ?
Max Reservation Limit As Percentage of Raw Channel Capacity
Syntax Description
usport The upstream port that has admission control enabled. percentage The optional percentage parameter specifies the overbooking rate that will be used when deciding the amount of bandwidth that is available to be guaranteed.
|
Note If percentage is left blank or set to 100%, the CMTS will only allow a total up to the real available upstream bandwidth to be guaranteed. If percentage is set to its maximum of 1000, then up to 10 times the real interface bandwidth may be "guaranteed". |
To determine if upstream admission control is configured and activated, enter the show running-config command in privileged EXEC mode and look for the cable interface configuration information. If upstream admission control is configured and enabled, an admission control entry appears in the show running-config command output, indicating the user-defined percentage of upstream channel capacity allowable. If upstream admission control is disabled, no admission control entry appears in the output.
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected a valid frequency for your router.
Differential encoding on the upstream is a digital encoding technique whereby a binary value is denoted by a signal change rather than a particular signal level. To enable differential encoding on upstream traffic to a specified cable interface, use the following command in cable interface configuration mode. Upstream differential encoding is enabled by default.
Router(config-if)# cable upstream usport differential-encoding
To determine if upstream differential encoding is activated, enter the show running-config command and look for the cable interface configuration information. If upstream differential encoding is enabled, a differential encoding entry appears in the show running-config output. If upstream differential encoding is disabled, no differential encoding entry appears in the output.
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected a valid frequency for your router.
The Cisco uBR7200 series CMTS uses forward error correction (FEC) to attempt to correct any upstream data that might have been corrupted. When FEC is activated, all CMs on the network also activate FEC.
|
Note Although upstream FEC is an option, Cisco recommends that you use upstream FEC. FEC is activated by default and should not be disabled. |
Router(config-if)# cable upstream usport fec
To verify whether FEC is activated or deactivated, enter the more system:running-config command and look for the cable interface configuration information. If FEC is enabled, an FEC entry appears in the show running-config command output. If FEC is disabled, no FEC entry appears in the output.
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected a valid frequency for your router.
Each upstream port must be activated to enable upstream data transmission from the CMs on the HFC network to the Cisco uBR7200 series CMTS.
|
Note The upstream cable interface does not operate until you either set a fixed upstream frequency or create and configure a spectrum group. Refer to the "Setting the Upstream Frequency" section on for details. |
To activate the upstream ports, use the following commands in global configuration mode.
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)# interface cable slot/port | Specifies a cable interface and enters cable interface configuration mode. |
Step 2 | Router(config-if)# no cable upstream usport shutdown | Enables upstream data traffic. |
To determine if the upstream ports are activated or deactivated, enter the show interface cable command for the upstream port just configured:
Router# show interface cable5/0
Cable5/0 is up, line protocol is up
Hardware is BCM3210 FPGA, address is 00e0.1e5f.7a60 (bia 00e0.1e5f.7a60)
Internet address is 1.1.1.3/24
MTU 1500 bytes, BW 27000 Kbit, DLY 1000 usec, rely 255/255, load 1/255
Encapsulation, loopback not set, keepalive not set
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:25, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Queuing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sea, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
10878 packets input, 853740 bytes, 0 no buffer
Received 3679 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
5401 packets output, 645885 bytes, 0 underruns
0 output errors, 0 collisions, 9 interface resets
0 output buffer failures, 0 output buffers swapped out
| Command | Purpose | |
|---|---|---|
Step 1 |
| Set the minimum number of frequency adjustment packets required to justify changing the upstream frequency adjustment method as a percentage. Acceptable range is 10 to 100 percent. |
Step 2 |
| Return to enable (privileged EXEC) mode. |
To return the automatic upstream frequency adjustment percentage to the default value of 30 percent, enter the following command in cable interface configuration mode:
Router(config-if)# no cable upstream usport frequency-adjust averaging
To determine if upstream frequency adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream frequency adjustment is enabled, frequency adjustment entries are displayed in the show running-config output. If frequency adjustments are disabled, no frequency adjustment entry displays in the output.
Perform these steps if you are having difficulty with verification:
1. Ensure the cable connections are not loose or disconnected
2. Ensure the cable interface line card is firmly seated in its chassis slot.
3. Ensure the captive installation screws are tight.
4. Verify that you have entered the correct slot and port numbers; you selected a valid frequency for your router.
| Command | Purpose |
|---|---|
| Sets the minimum power adjustment in dB that allows continued ranging status. Valid values are 2 to 15 dB. Default = 2 dB. |
| Sets the minimum number (percentage) of power-adjustment packets required to justify changing the upstream power rating. Valid values are 10 to 100 percent. Default = 30 percent. |
| Sets the power-adjustment threshold in dB. Valid values are 0 to 2 dB. Default = 1 dB. |
| Returns to enable (privileged EXEC) mode. |
To return the automatic upstream power-adjustment ranging value to the default of 2 dB, enter the following command in cable interface configuration mode:
Router(config-if)#no cable upstream usport power-adjust continue
To return the automatic upstream power-adjustment noise value to the default of 30 percent, enter the following command in cable interface configuration mode:
Router(config-if)# no cable upstream usport power-adjust noise
To return the upstream power-adjustment threshold value to the default of 1 dB, enter the following command in cable interface configuration mode:
Router(config-if)# no cable upstream usport power-adjust threshold
To determine if upstream power adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream power adjustment is enabled, any or all three of the continue, noise, and threshold power-adjustment entries appear in the show running-config command output. If all three upstream power adjustments are disabled, no power-adjustment entry appears in the show running-config command output.
The scrambler on the upstream RF carrier enables CMs on the HFC network to use built-in scrambler circuitry for upstream data transmissions. The scrambler circuitry improves reliability of the upstream receiver on the cable interface line card.
|
Caution The upstream scrambler is activated by default and should not be disabled under normal circumstances. Disabling it can result in corrupted packets. Disable it only for prototype modems that do not support the upstream scrambler. |
Router(config-if)# cable upstream usport scrambler
To determine if the upstream scrambler is activated, enter the more system:running-config command and look for the cable interface configuration information. Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected a valid frequency for your router.
| Command | Purpose |
|---|---|
| Sets the minimum timing adjustment that allows continued ranging status. Valid second values are 2 to 64 seconds. Default = 2 seconds. |
| Sets the timing adjustment threshold value in seconds. Valid second values are 1to 32 seconds. Default = 1 second. |
| Returns to enable (privileged EXEC) mode. |
To return the upstream time-adjustment ranging value to the default of 2 seconds, enter the following command in cable interface configuration mode:
Router(config-if)# no cable upstream usport time-adjust continue
To return the upstream time adjustment threshold value to the default of 1 second, enter the following command in cable interface configuration mode:
Router(config-if)# no cable upstream usport time-adjust threshold
To determine if upstream timing adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream timing adjustment is enabled, either or both of the continue and threshold timing-adjustment entries appear in the show running-config command output. If both the continue and threshold upstream timing adjustments are disabled, no timing adjustment entry appears in the show running-config command output.
|
Tip Perform the following steps if you are having difficulty with verification: |
Step 2 Verify that the cable interface line card is firmly seated in its chassis slot
Step 3 Verify that the captive installation screws are tight.
Step 4 Confirm that you have entered the correct slot and port numbers.
.
You can configure rate limiting and traffic shaping on a DOCSIS upstream channel. This delays the scheduling of the upstream packet, which in turn causes the packet to be buffered on the cable CPE device, instead of being dropped. This allows the user's TCP/IP stack to pace the application traffic appropriately and approach throughput commensurate with the subscriber's defined QoS levels.
To configure this, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)#[no] cable upstream <n1> rate-limit [token-bucket] | Enables or disables DOCSIS rate limiting or shaping on an upstream channel. <n1> depends on the number of upstream channels on the specific cable interface line card. |
Using Cisco IOS Release 12.0(5)T1 or higher, the software supports:
|
Tip Upstream grant shaping is per CM (SID). Shaping can be enabled or disabled for the token-bucket algorithm. |
|
Note Before the introduction of this feature, the CMTS would drop bandwidth requests from a CM it detected as exceeding its configured peak upstream rate. Such request dropping affects the throughput performance of IP-based protocols such as FTP, TCP, and SMTP. With this feature, the CMTS can shape (buffer) the grants for a CM that is exceeding its upstream rate, rather than dropping the bandwidth requests. |
Router# show interface c3/0 sid 1 counters
Sid Inpackets Inoctets Outpackets Outoctets Ratelimit Ratelimit
BWReqDrop DSPktDrop
1 67859 99158800 67570 98734862 2579 0
The DOCSIS-specified method of contention resolution for CMs wanting to transmit data or requests on the upstream channel is a truncated binary exponential backoff value, with the initial backoff window and the maximum backoff window controlled by the CMTS. The Cisco uBR7200 series CMTS specifies backoff window values for both data and initial ranging, and sends these values downstream as part of the Bandwidth Allocation Map (MAP) MAC message.
The values are configurable on the Cisco uBR7200 series software and are power-of-two values. For example, a value of 4 indicates a window between 0 and 15; a value of 10 indicates a window between 0 and 1023. You can set fixed start and end values for data backoff on the upstream ports, or you can set the upstream ports for automatic data backoff. You have the same options for ranging backoff. For both backoff windows, the default start value is 0; the default end value is 4. Valid values are from 0 to 15.
|
Note Cisco does not recommend that you adjust default values, but that you enable the automatic dynamic backoff algorithm. Refer to the "Configuring Dynamic Contention Algorithms (Cable Insertion Interval, Range, and Data Backoff)" section. |
| Command | Purpose | |
|---|---|---|
Step 1 |
| Optimizes the automatic setting for as many as 250 cable interfaces per upstream port. Sets manual values for data backoff windows only when operating with more than 250 cable interfaces per upstream port. |
Step 2 |
| Optimizes the automatic setting for as many as 250 cable interfaces per upstream port. Sets manual values for data backoff windows only when operating with more than 250 cable interfaces per upstream port. |
When considering whether to adjust backoff values, keep the following considerations in mind:
|
Note Upstream segments serving a relatively large number of cable interfaces (for example, more than 1600) might suffer recovery times greater than 10 minutes. |
To verify backoff window settings, enter the show controllers cable command for the upstream port you have just configured:
Router# show controllers cable5/0 u0
Cable5/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
part_id=0x3137, rev_id=0x03, rev2_id=0xFF
nb_agc_thr=0x0000, nb_agc_nom=0x0000
Range Load Reg Size=0x58
Request Load Reg Size=0x0E
Minislot Size in number of Timebase Ticks is = 8
Minislot Size in Symbols = 64
Bandwidth Requests = 0xFE
Piggyback Requests = 0xD
Invalid BW Requests= 0x2
Minislots Requested= 0x2963
Minislots Granted = 0x2963
Minislot Size in Bytes = 16
Map Advance = 4000 usecs
UCD Count = 32964
DES Ctrl Reg#0 = C000C043, Reg#1 = 0
Use the commands below to enter the upstream channel width in hertz (Hz). For NTSC operations, valid values are 200000 Hz (160 kilo symbols per second [ksps]), 400,000 Hz (320 ksps), 800,000 Hz (640 ksps), 1,600,000 Hz (1280 ksps), and 3,200,000 Hz (2560 ksps). The default is 1,600,000 Hz.
If no acceptable channels of the specified width are found, the spectrum management card automatically begins to scan the upstream spectrum for the next largest available channel width; for example, if the spectrum management card is unable to find a usable 1.6 MHz upstream channel, it automatically begins searching for usable 800 kHz channels.
|
Caution Higher symbol rates are more susceptible to RF noise and interference. If you use a symbol rate or modulation format beyond the capabilities of your HFC network, you might experience packet loss or loss of cable interface connectivity. |
|
Note For QAM-16 channel widths of 400 kHz (320 ksps) or greater, Cisco recommends that you use QAM-16 modulation for long and short data, and that you use QPSK for request, initial, and station communications. For QAM-16 channel widths of 200 kHz (160 ksps), all communication must be able to use QAM-16. That is, 160 ksps with QAM-16 requires an exceptional signal-to-noise ratio (SNR) in your upstream channels. When you use QAM-16 for request, initial, and station maintenance messages with channel widths greater than 400 kHz, the QAM-16 preamble and message data take longer to transmit than the QPSK format. |
|
Note To set the upstream channel width, use the following commands in cable interface configuration mode. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config-if)# cable upstream usport channel-width width | Enters the channel width for your upstream RF carrier in Hz. |
Step 2 | Router(config-if)# no cable upstream usport channel-width | Returns the channel width to its default setting of 1,600,000 Hz. |
For additional information about channel width and minislot size, refer to the Cable Radio Frequency (RF) FAQs on Cisco.com.
To verify the current value of the upstream channel width, enter the show controllers cable command for the upstream port you just configured. A sample follows below:
Router# show controllers cable5/0 u0
Cable5/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
Perform these steps if you are having difficulty with verification:
Step 2 Use a recommended or previously tested modulation profile. It is not uncommon to create a modulation profile that does not allow cable interface-to-headend communication. Because each message type is individually specified, some messages might not work.
Step 3 Verify using IP ping packets of varying lengths (64 to 1500 bytes). Ping from the headend to the cable interface.
Step 4 Verify with your cable interface vendor that your CM software is fully certified or compatible with DOCSIS 1.0 and extensions, as appropriate.
The upstream channel frequency of your RF output must be set to comply with the expected input frequency of your Cisco cable interface line card. To configure upstream channel frequencies, perform one of the following tasks:
|
Note You can also select a default that does not set a specific fixed value. |
|
Note The upstream port is frequency agile. If you define spectrum groups, the frequency can change while the interface is up and carrying traffic. |
A modulation profile consists of a table of physical layer characteristics for the different types of upstream bursts; for example, initial maintenance, long grant, request/data, request, short grant, and station maintenance.
|
Note The upstream cable interface does not operate until you either set a fixed upstream frequency or create
and configure a spectrum group. If you are setting a fixed upstream frequency, make sure that the frequency selected does not interfere with the frequencies used for any other upstream applications running on the cable plant. |
To set a fixed upstream frequency, use the following commands in cable interface configuration mode.
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config-if)# cable upstream usport frequency up-freq-hz | Enters the fixed center frequency for your upstream RF carrier in Hz. |
Step 2 | Router(config-if)# no cable upstream usport shutdown | Places the upstream port in the "admin up" state. |
|
Tip For National Television Standards Committee (NTSC) operations, valid ranges are 5000000 to 42000000 Hz. |
|
Caution Some cable systems cannot reliably transport frequencies near these band edges. The wider the upstream channel (in MHz), the more difficulty you might have. Enter a center frequency between 20 and 38 MHz if you have difficulty. |
|
Note You can also select a default that does not set a specific fixed value. The Cisco uBR7200 series software instructs the cable interfaces to use this frequency as the center frequency. |
To verify the current value of the upstream frequency, enter the show controllers cable command for the upstream port you have just configured:
Router# show controllers cable5/0 u0
Cable5/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
|
Note The upstream frequency displayed in the show controllers cable command output might not match the frequency that you entered when you set the upstream frequency. The Cisco uBR7200 series CMTS might select an upstream frequency close to the frequency you entered that offers better performance. The Cisco uBR7200 series CMTS selects the closest frequency available. |
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you have selected a valid frequency for your router.
The Cisco uBR7200 series CMTS controls the output power levels of CMs to meet the desired upstream input power level. The nominal input power level for the upstream RF carrier is specified in decibels per millivolt (dBmV). The default setting of 0 dBmV is the optimal setting for the upstream power level.
The valid range for the input power level depends on the data rate. At 1.6 MHz, the valid range is -10 to 25 dBmV. If your power levels operate at greater than the maximum valid level, use an inline attenuator to bring the power level to within the valid range.
|
Caution If you increase the input power level, CMs on your HFC network increase their transmit power level. This increases the carrier-to-noise ratio (C/N) on the network, but also increases distortion products. Composite Second Order Beat (CSO) and Composite Triple Beat (CTB) values worsen by 2 dB for every 1 dB-increased C/N. The return path laser immediately enters a nonlinear mode called clipping, and all communication becomes unreliable. Many return lasers send short bursts above the clipping thresholds and fail on longer or successive bursts. You should not adjust your input power level by more than 5 dB in a 30-second interval. If you increase the power level by more than 5 dB within 30 seconds, cable interface service on your network is disrupted. If you decrease the power level by more than 5 dB within 30 seconds, cable interfaces on your network are forced offline. |
|
Note When you run the cable upstream 0 power-level command, Cisco recommends that the adjacent channel not have a large variation. The recommended maximum input power variance is 5 to 6 dBmV. |
Router(config-if)# cable upstream usport power-level dbmv
To verify the current value of the upstream input power level, enter the show controllers cable command for the upstream port you have just configured:
Router# show controllers cable5/0 u0
Cable5/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
Perform these steps if you are having difficulty with verification:
1. Verify that the upstream amplitude of an optimal RF carrier (injected at the fiber node reference input point) reaches the cable interface line card input point at a consistent level (node-to-node and port-to-port).
2. Verify that this absolute level, as installed, matches both the design and software settings on the Cisco uBR7200 series CMTS.
|
Note Software adjustments of 1 to 3 dB can be used to adjust for minor variations in measurement or setup and port-to-port calibration differences. These adjustments can significantly improve cable interface performance, especially in marginal situations. Larger adjustments should be made in conjunction with spectrum analyzer support at the headend or distribution hub. |
Router(config-if)# cable upstream usport minislot-size size
For additional information about channel width and minislot size, refer to the Cable Radio Frequency (RF) FAQs on Cisco.com.
To verify upstream minislot size, enter the show controllers cable command for the upstream port you have just configured:
Router# show controllers cable5/0 u0
Cable5/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
part_id=0xFFFF, rev_id=0xFF, rev2_id=0xFF
nb_agc_thr=0x0000, nb_agc_nom=0x0000
Range Load Reg Size=0x58
Request Load Reg Size=0x0E
Minislot Size in number of Timebase Ticks is = 8
Minislot Size in Symbols = 64
Bandwidth Requests = 0xFE
Piggyback Requests = 0xD
Invalid BW Requests= 0x2
Minislots Requested= 0x2963
Minislots Granted = 0x2963
Minislot Size in Bytes = 16
Map Advance = 4000 usecs
UCD Count = 32964
DES Ctrl Reg#0 = C000C043, Reg#1 = 0
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected a valid frequency for your router.
Upstream traffic shaping, available on the DOCSIS upstream channel, delays the scheduling of the upstream packet, which in turn causes the packet to be buffered on the cable customer premises equipment (CPE) device, instead of being dropped. This allows the user's TCP/IP stack to pace the application traffic appropriately and approach throughput commensurate with the subscriber's defined quality of service (QoS) levels.
The CMs are buffered without incurring TCP-related timeouts and retransmits. This enables the CMTS to enforce the peak upstream rate for each CM, without degrading overall TCP performance for the subscriber CPEs. Upstream grant shaping is per cable interface (per service ID (SID)).
Token-bucket policing with shaping is the per-upstream default rate-limiting setting at the CMTS. Shaping can be enabled or disabled for the token-bucket algorithm.
| Command | Purpose | |
|---|---|---|
Step 1 |
| Enables traffic shaping for the specified upstream cable interface.
Enables traffic shaping for the upstream cable interface employing the token-bucket policing algorithm. With this command the Cisco uBR7200 series CMTS automatically drops packets in violation of allowable upstream bandwidth. |
Step 2 | Router(config-if)# | Exits back to the EXEC mode so that you can verify upstream traffic shaping. |
To disable upstream traffic shaping for an upstream port, enter the following command in cable interface configuration mode:
Router(config-if)# no cable upstream usport rate-limit
The software supports:
|
Tip Upstream grant shaping is per CM (per service ID (SID)). Shaping can be enabled or disabled for the token-bucket algorithm. |
|
Note Before the introduction of this feature, the CMTS would drop bandwidth requests from a CM it detected as exceeding its configured peak upstream rate. Such request dropping affects the throughput performance of IP-based protocols such as FTP, TCP, and Simple Network Management Protocol (SNMP). With this feature, the CMTS can shape (buffer) the grants for a CM that is exceeding its upstream rate, rather than dropping the bandwidth requests. |
Router# show interface c5/0 sid 1 counters
00:02:23: %ENVM-3-LASTENV: Cannot save environmental data
Sid Req-polls BW-reqs Grants Packets Frag Concatpkts
issued received issued received complete received
1 0 22 22 22 0 0
2 0 3 3 2 0 0
3 0 0 0 0 0 0
To determine if upstream traffic shaping is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream traffic shaping is configured and enabled, a traffic shaping entry appears in the show running-config output. If upstream traffic shaping is disabled, no cable upstream rate-limit appears in the output.
You can also perform the following tasks to verify that traffic shaping is enabled on the upstream channel:
Step 2 Use a regular rate-limiting algorithm on the upstream without rate shaping, and note the drops of the excess bandwidth requests from this CM when it exceeds its peak upstream rate.
Use the show interface cx/y sid counters verbose command to see the bandwidth request drops. Verify that the upstream rate received by that modem is less than its configured peak rate, due to the timeouts and backoffs produced by the drop in bandwidth requests. Enter the show interface cx/y service flow qos command to see the input rate at CMTS in bps.
Step 3 Enable grant shaping on the upstream channel by using the new shaping keyword extension to the token-bucket algorithm CLI command.
Step 4 Make the CM exceed its peak upstream rate by generating upstream traffic, and note the effect of grant buffering (shaping) at the CMTS. If you use CM-to-CMTS pings, there is a perceivable decrease in the frequency of the pings.
Let the pings run long enough to allow the averages at the CMTS to settle; then view the upstream rate received by this single modem. Use the show interface cx/y command and see the input rate in bps. This value should be close to the modem's peak upstream rate. Also note the drop counts for the modem's SID by using the show interface sid counters command, and verify that the CMTS no longer drops the bandwidth requests from the CM.
The bandwidth request drop count (from the previous nonshaping test) remains unchanged when upstream rate shaping is used, indicating that the CMTS is actually shaping (buffering) the grants for the modem. Verify that the input rate at the CMTS (from the single rate-exceeded CM) stabilizes close to the configured peak rate of 128 Kbps.
Perform these steps if you are having difficulty with verification:
Step 2 Ensure that the cable interface line card is firmly seated in its chassis slot.
Step 3 Ensure that the captive installation screws are tight.
Step 4 Verify that you have entered the correct slot and port numbers.
Step 5 Verify that you selected a valid frequency for your router.
This section builds on the required CM interface features documented earlier in this chapter. This section provides instructions for several optional CM interface configurations. These interface features pertain to heightened performance and security measures.
|
Note Default settings are typically adequate to configure optional features on the system. Change default settings only with careful prior analysis. |
| Section | Purpose |
Allows the Cisco uBR7200 series CMTS to issue cable Address Resolution Protocol (ARP) requests on behalf of CMs on the same cable network subnet. | |
Specifies a MAC address on the cable network for which interception capabilities are to be activated. |
Cable proxy ARP allows the Cisco uBR7200 series CMTS to issue cable ARP requests on behalf of CMs on the same cable network subnet.
|
Note Because the downstream and upstreams are separate interfaces, modems cannot directly perform ARP with other modems on the cable plant. |
|
Note The default values for the commands used in this configuration task are adequate in most cases to configure the Cisco uBR7200 series CMTS. |
To activate cable proxy ARP for host-to-host communications, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)# cable proxy-arp | Enables proxy ARP on the cable interface. This is the default. |
To verify if cable proxy ARP has been activated or deactivated, enter the more system:running-config command and look for the cable interface configuration information. If cable proxy ARP has been activated, it does not appear in the output. If cable proxy ARP has been deactivated, it appears in the output as no cable proxy-arp.
Router# more system:running-config
Building configuration...
Current configuration:
!
interface cable5/0
ip address 1.1.1.1 255.255.255.0
no keepalive
no cable proxy-arp
cable downstream annex B
cable downstream modulation 64qam
cable downstream interleave-depth 32
cable downstream symbol-rate 5056941
cable upstream 0 frequency 15008000
no cable upstream 0 shutdown
|
Tip If you are having difficulty with verification, make sure that you entered the correct port and cable interface line card slot number when you activated cable proxy ARP. |
To activate packet intercept functionality, use the following commands in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)# cable intercept xxxx.xxxx.xxxx | Specifies a MAC address on the cable network for which interception capabilities are to be activated. There is a limit of 10 MACs. |
Router(config-if)# no cable intercept xxxx.xxxx.xxxx | Disables interception after it is enabled. |
The command to create a subinterface over a cable interface is the same as that defined by Cisco IOS for other software applications:
interface cable x/y.n
where x is the slot number, y is the port number, and n is the subinterface number.
Each created subinterface is assigned a software IDB. The layer 3 packet arriving over a physical cable interface must be assigned an appropriate software IDB to which it belongs. Since each packet that is received over a cable interface is prepended with its associated SID, this can be extracted from the packet and used as the key to find the associated software IDB. The defined cmts_sid_instance_t structure holds information pertaining to the SID and is extended to include the associated software IDB pointer.
The IP address stored in the DHCP reply is matched for its subnet value against the subnet value configured for each of the subinterfaces over the physical cable interface. The subnet information is derived by combining the IP address and the mask value available in the software IDB structure.
The linked list of software IDBs can be accessed from the hardware IDB associated with the physical cable interface. At the time of CM registration, the software IDB address is initialized to null as the mapping is unknown at first.
|
Tip In current releases of software, the SID-to-subinterface mapping is done based on the DHCP-assigned IP address and is not user configurable. |
The following example shows how to define a subinterface on the cable5/0:
interface cable5/0 ! No IP address ! MAC level configuration only
! first subinterface interface cable5/0.1 description Management Subinterface ip address 10.255.1.1 255.255.255.0 cable helper-address 10.151.129.2 ! second subinterface interface cable5/0.2 ip address 10.279.4.2 255.255.255.0 cable helper-address 10.151.129.2 ! third subinterface interface cable5/0.3 ip address 10.254.5.2 255.255.255.0 cable helper-address 10.151.129.2
The following example shows how to define subinterfaces on a bundle master and define Layer 3 configurations for each subinterface. In this example, the interfaces int c5/0 and int c4/0 are bundled.
int c5/0 ! No IP address ! MAC level configuration only cable bundle 1 master int c4/0 ! No IP address ! MAC layer configuration cable bundle 1 ! first subinterface int c5/0.1 ip address 10.22.64.0 255.255.255.0 cable helper-address 10.4.1.2 ! second subinterface int c5/0.2 ip address 10.12.39.0 255.255.255.0 cable helper-address 10.4.1.2 ! third subinterface int c5/0.3 ip address 10.96.3.0 255.255.255.0 cable helper-address 10.4.1.2
Cable interface bundling allows you to reduce the number of subnets consumed per Cisco uBR7200 series. Multiple cable interfaces can share a single IP subnet. An IP subnet is required for each bundle. You can bundle all cable interfaces on a Cisco uBR7200 series into a single bundle.
Using the CLI, first configure a master interface for a cable interface bundle. The master interface has an IP address assigned and is visible for IP routing functionality. After you configure the master interface, add additional cable interfaces to the same interface bundle. Those interfaces must not have an IP address assigned. You can also configure multiple bundle interfaces.
You can configure up to four interface bundles. In each bundle, specify exactly one interface as the master interface, using the "master" keyword. In the case of a subinterface over a cable bundle, \Qx' is the interface number of the bundle master [1]. The subinterface number starts from 1.
|
Caution Configure an IP address on the master interface only. An attempt to add an interface to a bundle will be rejected if an IP address is configured and the interface is not specified as a master interface. |
When bundling cable interfaces, only the interface configured to be the bundle master is allowed to have subinterfaces. An interface that has subinterface(s) defined over it will not be allowed to be part of a bundle.
MIB objects on cable interface bundles are not supported as of the date of this publication.
|
Tip Generic cable interface configuration such as source verify or ARP handling will apply to subinterfaces as well. |
|
Note If a physical interface goes down, the associated subinterface will also go down. If the subinterface is defined over the cable bundle and the bundle master is shut down or removed, no data packets will be sent to any of the subinterfaces defined over it. Packets will still be received from non-master interfaces, but will be dropped. |
Use the following commands to configure and view cable interface bundles in privileged EXEC mode:
| Command | Purpose |
|---|---|
Router(config-if)# cable bundle n master | Configures the interface n to be the master interface in a bundle. Valid range is 1 to 255. |
Router# show cable bundle n forwarding-table | Displays the forwarding table for the specified interface. |
Use the cable bundle interface configuration command to configure a cable interface to belong to a bundle. Specify the bundle identifier—1 to 255. Optionally define the specified interface as the master.
Specify IP networking information, including IP address, routing protocols, and switching modes, on the bundle master. Do not specify generic IP networking information on bundle slave interfaces.
If you attempt to add an interface to a bundle as non-master interface and an IP address is assigned to this interface, the command will fail. You must remove the IP address configuration before you can add the interface to a bundle.If you have configured an IP address on a bundled interface and the interface is not the master interface, a warning message appears.
Specify generic (that is, not downstream or upstream related) cable interface configurations, such as source-verify or ARP handling, on the master interface. Do not specify generic configuration on non-master interfaces.
If you configure an interface as part of a bundle and it is not the master interface, all generic cable configuration for this interface is removed. The master interface configuration will then apply to all interfaces in the bundle.
If you shut down or remove the master interface in a bundle, no data packets are sent to any of the interfaces in this bundle. Packets will still be physically received from non-master interfaces which have not been shut down, but those packets will be discarded. This means that cable modems connected to those interfaces will not be disconnected immediately, but CMs coming online will not be able to obtain an IP address, download their DOCSIS configuration file, or renew their IP address assignment if the DHCP lease expires.
If you shut down a slave interface, only the specific interface is affected.
In the following configuration example, interface 25 is configured as the master interface in the bundle:
Router(config-if)# cable bundle ? <1-255> Bundle number Router(config-if)# cable bundle 25 ? master Bundle master <cr> Router(config-if)# cable bundle 25 master ? <cr> Router(config-if)# cable bundle 25 master Router(config-if)# 07:28:17: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to down 07:28:18: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to up Router# show cable bundle 25 forwarding-table MAC address Interface 0050.7366.17ab Cable3/0 0050.7366.1803 Cable3/0 0050.7366.1801 Cable3/0
The following example shows an error message you receive if you try to configure an interface with an IP address that is not the master interface:
Router(config-if)# cable bundle 5 Please remove ip address config first then reenter this command
To display the forwarding table for a specified interface, use the show cable bundle command in privileged EXEC mode. A sample is shown below:
Router# show cable bundle 25 forwarding-table MAC address Interface 0050.7366.17ab Cable3/0 0050.7366.1803 Cable3/0 0050.7366.1801 Cable3/0
The following example shows how to bundle a group of physical interfaces. In this example, the interfaces int c5/0 and int c4/0 are bundled.
int c5/0 ip address 209.165.200.225 255.255.255.0 ip address 209.165.201.1 255.255.255.0 secondary cable helper-address 10.5.1.5 ! MAC level configuration cable bundle 1 master int c4/0 ! No IP address ! MAC layer configuration only cable bundle 1
The following example shows how to configure interface 25 to be the master interface:
Router(config-if)# cable bundle 25 master Router(config-if)# 07:28:17: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to down 07:28:18: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to up The following example shows the error message you get if you try to configure an interface with an IP address that is not the master interface: Router(config-if)# cable bundle 5 Please remove ip address config first then reenter this command Router(config-if)#
Payload Header Suppression (PHS) is a new feature in the DOCSIS1.1 MAC driver. The PHS feature is used to suppress repetitive or redundant portions in packet headers before transmission on the DOCSIS link. The upstream receive driver is now capable of restoring headers suppressed by CMs, and the downstream driver is capable of suppressing specific fields in the packet header before forwarding the frame to the CM.
| Command | Purpose |
|---|---|
show interface cable x/0 service-flow [sfid] phs | Displays cable interface information. |
debug cable error | Displays errors that occur in the cable MAC protocols. To disable debugging output, use the no form of the command. |
debug cable phs | Displays the activities of the PHS and restoration driver. The no form of this command disables debugging output. |
You can set additional IP parameters to enable downstream echoing of upstream data. This section contains two procedures to configure these optional IP parameters:
|
Note The default values for the commands used in these configuration steps are adequate in most cases to configure the Cisco uBR7200 series CMTS. |
The Cisco uBR7200 series CMTS echos IP multicast packets by default. To activate IP multicast echo if it has been previously disabled, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)# cable ip-multicast-echo | Enables IP multicast echo. This is the default. |
To disable IP multicast echo, enter the no cable ip-multicast-echo command in cable interface configuration mode.
To determine whether IP multicast echo is activated or deactivated, enter the more system:running-config command, and look for the cable interface configuration information. If IP multicast echo is activated, there is no notation in the output, because this is the default setting. If IP multicast echo is deactivated, a notation appears in the output:
Router# more system:running-config
Building configuration...
Current configuration:
!
interface cable5/0
ip address 1.1.1.1 255.255.255.0
no keepalive
no cable ip-multicast-echo
cable downstream annex B
cable downstream modulation 64qam
cable downstream interleave-depth 32
cable upstream 0 frequency 15008000
no cable upstream 0 shutdown
|
Tip If you are having difficulty with verification, make sure that you entered the correct slot and port numbers when you entered cable interface configuration mode. |
By default, the Cisco uBR7200 series CMTS does not echo IP broadcast packets. To activate IP broadcast echo, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
Router(config-if)# cable ip-broadcast-echo | Enables IP broadcast echo. |
To disable IP broadcast echo when it is enabled, enter the no cable ip-broadcast-echo command in cable interface configuration mode.
To determine whether IP broadcast echo is activated or deactivated, enter the more system:running-config command and look for a notation in the cable interface configuration information:
Router# more system:running-config
Building configuration...
Current configuration:
!
interface cable5/0
ip address 1.1.1.1 255.255.255.0 no keepalive cable ip-broadcast-echo cable downstream annex B cable downstream modulation 64qam cable downstream interleave-depth 32 cable upstream 0 frequency 15008000 no cable upstream 0 shutdown
Posted: Fri Jun 28 16:48:30 PDT 2002
All contents are Copyright © 1992--2002 Cisco Systems, Inc. All rights reserved.
Important Notices and Privacy Statement.