Usage Guidelines

ACFE uses the EIR demand value as weight to allocate bandwidth between bonding groups. The EIR demand value is calculated dynamically base on service flow priority, unless this command is configured.

Usage Guidelines

Configure the Fairness Across DOCSIS Interfaces feature on the MC, IC, or WB interfaces.

It is recommended that you clear the CIR reservation above the legacy “reservable” bandwidth before disabling Fairness Across DOCSIS Interfaces feature. This is to prevent any CIR over-subscription after disabling Fairness Across DOCSIS Interfaces feature.

Usage Guidelines

The cable acfe max-bonus-bandwidth command configures the maximum usable bonus bandwidth. After disabling Fairness Across DOCSIS Interfaces feature, this configuration is retained. However, it will not be used.

Usage Guidelines

The cable acfe max-eir-ratio command configures the maximum EIR ratio between the BE bandwidth among adjacent BGs.

The failure to maintain the maximum EIR ratio may reduce the guaranteed bandwidth rate for the BE traffic to zero. This may lead to rejection of unicast CIR flows.

Usage Guidelines

The threshold counters are set to zero when the resource is reconfigured.

An important concept for system resources that are set with this command (CPU and memory) is the concept of dampening . Without dampening, and when admission control is configured for the first time, the system resource check is unsuccessful if the current value exceeds the critical threshold. When this happens, the system resource check subsequently succeeds only if the current value drops below the major threshold.

Note	When the minor threshold value set with Num1 or a major threshold value set with Num2 is crossed, the Cisco CMTS router sends an alarm (SNMP trap, when supported). When the critical threshold value set with Num3 is crossed, the Cisco CMTS router drops the call request.

This dampening approach helps prevent significant fluctuations in the outcome of resource checks. For example, if the critical threshold were 80 percent and the current values fluctuated between 79 and 81 percent, this scenario would lead to an alternate success then failure event without dampening. The first check would succeed, the second check would fail, and so forth.

For additional Admission Control feature information, refer to the Admission Control for the Cisco Cable Modem Termination System document on Cisco.com.

Usage Guidelines

Downstream bandwidth settings support all interfaces on the Cisco CMTS router through global configuration.

Downstream bandwidth settings can be further refined per-interface or per-upstream, the latter of which provides optimal downstream Admission Control granularity on the Cisco CMTS router.

When interface-level downstream configuration is used in combination with global configuration, then the interface configuration supersedes global configuration.

Note	The critical keyword is not present for the upstream throughput resource management with the Cisco Service Flow Admission Control feature.

Note	The minor threshold level cannot be greater than the major threshold level.

Usage Guidelines

At least one event type must be configured to enable admission control on the Cisco CMTS router.

For additional Admission Control feature information, refer to the Admission Control for the Cisco Cable Modem Termination System document on Cisco.com.

Usage Guidelines

This command allows the user to define the maximum reserved bandwidth per bonding group. The default maximum reserved bandwidth value is 80 percent. However the user can choose to configure a higher (up to 96 percent) or lower reserved bandwidth so that there is bandwidth allocated for zero committed information rate (CIR) best effort traffic.

Usage Guidelines

By default, PacketCable Emergency 911 calls are given priority on the Cisco CMTS. This priority may be preempted or removed from the Cisco CMTS router with non-standard configuration of the Service Flow Admission Control feature.

For additional information for Service Flow Admission Control beginning in Cisco IOS Release 12.3(21)BC, refer to the Service Flow Admission Control for the Cisco Cable Modem Termination System document on Cisco.com.

Usage Guidelines

Upstream bandwidth settings support all interfaces on a Cisco CMTS router through global configuration.

Upstream bandwidth settings can be further refined on a per-interface or per-upstream basis using interface configuration mode. Per-upstream settings provide the optimal upstream admission control granularity on the Cisco CMTS router.

When interface or per-upstream configuration is used in combination with global configuration, then interface or per-upstream configuration supersedes global configuration. Per-upstream configuration also supersedes per-interface configuration.

Note	The critical keyword is not present for the upstream throughput resource management with Cisco Admission Control.

Note	The minor threshold level cannot be greater than the major threshold level.

Usage Guidelines

The details of this command vary according to the bucket number and application type being mapped to a service flow on the Cisco CMTS router. This command overrides default service flow admission control settings on the Cisco CMTS.

Best Effort

The best effort CIR service flow rule may be applicable to both upstream and downstream. However, in the case of upstream service flows, in most cases, the same service flow may map both the rules.

For best effort, there is also the sched-type keyword option that applies to upstream service flows. This best effort scheduling type rule is applicable only for upstream service flows.

Service Classes

DOCSIS 1.1 introduced the concept of service classes. A service class is identified by a service class name. A service class name is a string the CMTS router associates with a QoS parameter set. One of the objectives of using a service class is to allow the high-level protocols to create the service flows with the desired QoS parameter set. Using a service class is a convenient way to bind the application with the service flows. The rules provide a mechanism to implement such binding.

Note the following factors when using the service-class keyword:

• Service classes are separately configured using the cable match command to provide the QoS for multicast traffic. This step maps a bucket using a rule to allocate bandwidth for multicast traffic.
• A named service class may be classified into any application type.
• Up to ten service class names may be configured per application type. Attempting to configure more than ten service classes results in an error message.

For additional information, see the Service Flow Admission Control feature documentation on Cisco.com.

Usage Guidelines

This bucket name appears in supporting show and debug commands along with the default bucket number.

For additional information, see the Service Flow Admission Control feature documentation on Cisco.com.

Usage Guidelines

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 so that the Cisco CMTS router can perform IP address resolution on the downstream path.

Occasionally, you might want to use the no cable arp and clear arp-cache commands to block out new ARP requests and clear the existing ARP table. In this situation, the Cisco CMTS router will retain the ARP addresses of currently online CMs (CMs with a known IP address) and will continue to send ARP requests for those CMs when those ARP entries time out or are cleared, so that those CMs can continue to remain online. ARP requests for CMs that are currently offline and for any other unknown IP addresses, however, will remain blocked until ARP requests are reenabled on the downstream using the cable arp command.

Note	Using the no cable arp and no cable proxy-arp commands shifts all responsibility for the management of the IP addresses used by CMs and CPE devices to the DHCP server and provisioning system.

Tip

You can expect to see a temporary spike in CPU usage after initially giving the no cable arp command, because of the need to verify CPE IP addresses. CPU usage drops after the router has verified and learned all of the CPE IP addresses that are currently online. (This same situation occurs after initially enabling the cable source-verify dhcp command, because the router must send a DHCP LEASEQUERY request for every unknown CPE IP address.)

Note	Starting from IOX-XE 3.15 OS, this command is integrated into bundle interface configuration mode for cBR Series Converged Broadband Routers.

Usage Guidelines

Viruses, worms, and theft-of-service attacks can generate a large volume of ARP requests on a cable interface. In some situations, the volume of ARP traffic can become so large that it throttles all other traffic.

To control the number of ARP replies and ARP requests that are allowed for each SID on a cable interface, use the cable arp filter command. This command configures the interface so that it accepts only a certain number of ARP reply or request packets per a specified time period. If a SID generates more ARP packets than what is allowed, the cable interface drops the excessive traffic.

By default, no ARP filtering is done. ARP filtering is enabled on individual cable interfaces, and you can choose to filter ARP packets only on the specific cable interfaces that require it. You can further choose to filter only ARP request packets, only ARP reply packets, or both. You can configure different threshold values on each interface, allowing you to customize the feature for each interface’s traffic patterns.

If using bundled cable interfaces, the Cable ARP Filtering feature is configured separately on the primary and subordinate interfaces. This allows you to configure the feature only on the particular interfaces that require it.

Note	Cisco IOS Release 12.3(9a)BC introduces enhanced command option syntax for the cable arp filter command, where number and window-size values are optional for reply-accept and request-send settings.

Note

Disabling the cable ARP filtering feature, using the no cable arp filter command, does not reset the ARP packet counters. The ARP packet counters do not increment when cable ARP filtering is disabled, but the counters retain their current values until the interface counters are specifically cleared, using the clear counters command.

The Linksys Wireless-B Broadband Router BEFW11S4 version 4 with 1.44.2 firmware incorrectly sends its own ARP reply packet for every ARP request packet it receives, instead of replying only to the ARP requests that are specifically for itself. Customers with these routers should upgrade the firmware to the latest revision to fix this bug. To upgrade the firmware, go to the download section on the Linksys web site.

Note	Starting from IOX-XE 3.15 OS, this command is integrated into bundle interface configuration mode for cBR Series Converged Broadband Routers.

Usage Guidelines

The attribute mask comprises 32 attributes and each attribute represents a single bit in the mask. You can configure a provisioned attribute mask for each channel and provisioned bonding group to assign values to the operator-defined binary attributes, or to override the default values of the specification-defined attributes. The operator may configure, in the CM configuration file, a required attribute mask and a forbidden attribute mask for a service flow. Additionally, in a CM-initiated dynamic service request, the CM can include a required attribute mask and a forbidden attribute mask for a service flow.

Usage Guidelines

Note	To use the cable bgsync command, you must configure the service internal command in global configuration mode. Use the cable bgsync command carefully as it can impact the CPU utilization.

For more information about MIB objects that are synchronized during background synchronization, see the Cisco CMTS Universal Broadband Router Series MIB Specifications Guide 12.2SC.

Usage Guidelines

Use the cable bgsync active command to activate the background synchronization process.

In Cisco uBR10012 and Cisco 7200 Series routers, SNMP objects use interprocess communication (IPC) to access data between the line card and the route processor (RP). When SNMP queries are sent to a Cisco CMTS with large number of modems configured, IPC takes a long time to retrieve the information from the line card and pass it on to the RP. This resulted in an increase in the SNMP response time. The background synchronization process slowly synchronizes the data between the line card and the RP. Therefore, when SNMP queries are sent to the Cisco CMTS, the Cisco CMTS returns the SNMP data from the RP. IPC requests are not sent to retrieve the data, thereby improving the SNMP performance.

In Cisco cBR Series routers, SNMP background synchronization features provides periodic background synchronization of DOCSIS MIB data from line card to Supervisor in order to improve the performance of the SNMP polling of these MIB tables. It is based on raw socket and uses TCP protocol.

The background synchronization process is enabled by default on the Cisco cBR-8, Cisco uBR10012, and Cisco 7200 Series routers.

For more information about the MIB objects that are synchronized during background synchronization, see the Cisco CMTS Universal Broadband Router Series MIB Specifications Guide 12.2SC. and Cisco cBR Series Converged Broadband Routers Troubleshooting and Network Management Configuration Guide.

Usage Guidelines

The cable bonding-group-id command is not needed for the wideband channels that will be received by the Scientific Atlanta DPC2505 or EPC2505 wideband cable modems.

The cable bonding-group-id command is used only for wideband channels that will be received by the Linksys WCM300-NA, WCM300-EURO, or WCM300-JP wideband cable modems.

Linksys WCM300 Cable Modem

For wideband channels that will be received by the Linksys WCM300-NA, WCM300-EURO, and WCM300-JP cable modems, the cable bonding-group-id command assigns a Bonding Group ID to a wideband-channel cable interface and configures the bonding group as a primary bonding group if the secondary keyword is not specified, or as a secondary bonding group if the secondary keyword is specified.

• A primary bonding group is a primary bonded channel.
• A secondary bonding group is a secondary bonded channel.

The primary bonded channel is the wideband channel on which the Linksys WCM300 modem receives all of its unicast traffic and some of its multicast traffic. The cable modem may identify the primary bonded channel and any secondary bonded channels to the CMTS at cable modem registration time. The DOCSIS configuration file may define the primary bonded channel for the CMTS to assign to the cable modem.

In addition to joining one primary bonded channel, the Linksys WCM300 may join up to two secondary bonded channels simultaneously in order to receive additional data streams. The DOCSIS configuration file may define the secondary bonded channels for the modem to pass to the CMTS. Secondary bonded channels are intended to receive multicast traffic such as broadcast video that is not available on the primary bonded channel.

For information on the TLV encodings that can be used in the DOCSIS configuration file to identify primary and secondary bonded channels, see the Cisco Cable Wideband Solution Design and Implementation Guide, Release 1.0 .

Note	If a wideband channel is specified as a primary or secondary bonded channel in the DOCSIS configuration file, it must be identically defined as a primary or secondary bonded channel in the CMTS active, running configuration file.

• If a wideband channel is configured with the cable bonding-group-id command or by default to be a primary bonded channel, the Linksys WCM300 modem will not register using it as one of its secondary bonded channels.
• If a wideband channel is configured with the cable bonding-group-id command to be a secondary bonded channel, the Linksys WCM300 modem will not register using it as its primary bonded channel.

Note

When a wideband channel is defined on a Wideband SPA, Cisco IOS software configures the wideband channel as a primary bonding group (primary bonded channel) and assigns a default ID to the bonding group. If a wideband channel is to be used as a secondary bonded channel, use the cable bonding-group-id command with the secondary keyword to specify that the channel is a secondary bonded channel.

If you specify a non-unique Bonding Group ID for the id_num argument, cable bonding-group-id displays an error message and does not modify the ID.

Usage Guidelines

Starting with Cisco IOS Release 12.2(33)SCE, the cable bonding-group-secondary command replaces the cable bonding-group-id command. If you upgrade from an earlier Cisco IOS Release to Cisco IOS Release 12.2(33)SCE and later, the cable bonding-group-id command will no longer change the bonding-group ID.

The cable bonding-group-secondary command is used only for wideband channels that are received by the Linksys WCM300-NA, WCM300-EURO, or WCM300-JP wideband cable modems.

Linksys WCM300 Cable Modem

For wideband channels that are received by the Linksys WCM300-NA, WCM300-EURO, and WCM300-JP cable modems, the show controllers Modular-Cable slot /subslot /controller wideband command displays the bonding group ID of a wideband-channel cable interface and the cable bonding-group-secondary command configures the bonding group as a secondary bonding group.

The primary bonded channel is the wideband channel on which the Linksys WCM300 modem receives all of its unicast traffic and some of its multicast traffic. The cable modem identifies the primary bonded channel and any secondary bonded channels to the CMTS at cable modem registration time. The DOCSIS configuration file defines the primary bonded channel for the CMTS to assign to the cable modem.

In addition to joining one primary bonded channel, the Linksys WCM300 joins up to two secondary bonded channels simultaneously in order to receive additional data streams. The DOCSIS configuration file defines the secondary bonded channels for the modem to pass to the CMTS. Secondary bonded channels are intended to receive multicast traffic such as broadcast video that is not available on the primary bonded channel.

For information on the TLV encodings that can be used in the DOCSIS configuration file to identify primary and secondary bonded channels, see Cisco Cable Wideband Solution Design and Implementation Guide, Release 1.0 .

Note	If a wideband channel is specified as a primary or secondary bonded channel in the DOCSIS configuration file, it must be identically defined as a primary or secondary bonded channel in the CMTS active, running configuration file.

The following points list the restrictions for configuring the wideband channel with the cable bonding-group-secondary command:

• If a wideband channel is not configured with the cable bonding-group-secondary command, the Linksys WCM300 modem may not use it as a secondary bonding group.
• If a wideband channel is configured with the cable bonding-group-secondary command to be a secondary bonded channel, the Linksys WCM300 modem may not use it as a primary bonded group.

Note

When a wideband channel is defined, the Cisco IOS software configures the wideband channel as a primary bonding group (primary bonded channel) and assigns a default ID to the bonding group. If a wideband channel is to be used as a secondary bonded channel, use the cable bonding-group-secondary command to specify that the channel is a secondary bonded channel.

Usage Guidelines

By default, the SNMP cache feature is activated. It can be enabled or disabled globally using the cable cache-snmp active command. It cannot be enabled or disabled per table currently. You can turn cache off if their polling strategy does not suit the cache principle so that cache will help on a sequential polling.

Usage Guidelines

This command resets any counters that were displayed from the last time the show controllers clock-reference command was used.

Note	This command is not supported on the SC train.

This command supports the Cisco CMTS clock feature set, which provides a synchronized clock for improved Voice-over-IP (VoIP) operations. The clock feature set requires one of the following configurations:

• A Cisco uBR10012 router with one or two TCC+ cards that are connected to an external national clock source.

Note	Beginning in Cisco IOS Release 12.3(23)BC, TCC+ is replaced with the DOCSIS Timing and Control Card (DTCC) and does not require to be connected to an extenal national clock source.

• A Cisco uBR7246 VXR router using a Cisco uBR-MC16S, Cisco uBR-MC16E, Cisco uBR-MC28C, or Cisco uBR-MC28C-BNC cable interface line card. The router must also be equipped with a Cisco cable clock card and be running Cisco IOS Release 12.1(1a)T1, Cisco IOS Release 12.1(2)EC1, or a later release. The Cisco cable clock card should be connected to an external national clock source.

Only these cable interface cards support the external clock card reference from a clock card to distribute that signal to CMs or set-top boxes (STBs) attached to the specific network segments. You can use other cable interface cards, such as the Cisco uBR-MC16C, with the clock card, but these other cable interfaces will not synchronize their downstream SYNC messages with the external clock source.

Each CM or STB must also support VoIP applications and the clock feature set. For example, the Cisco uBR924, running Cisco IOS Release 12.0(7)T or later releases, supports the clock card feature automatically.

Note

The show controllers clock-reference command might display compare errors on the Cisco uBR10012 router because there could be a slight delay at system startup before the clock cards synchronize with each other. These initial compare errors can be ignored and cleared with the cable clock clear-counters command.

Usage Guidelines

Use this command to configure DTI clocking mode.

This command may be stored in NVRAM as part of the DOCSIS Timing and Control Card (DTCC) configuration on the Cisco uBR10012 and Cisco uBR7225VXR routers.

Note	When the cable clock dti command or its no form is used to configure the DTI clock reference mode, the DTCC card on the Cisco uBR10012 router restarts and the cable modems may re-initialize or re-register.

Usage Guidelines

This command resets any counters that were displayed from the last time the show cable clock dti client command was used in DTI mode.

This command supports the Cisco CMTS clock feature set, which provides a synchronized clock for improved Voice-over-IP (VoIP) operations.

Usage Guidelines

This command overrides the default behavior of the clock card when the clock card is in holdover mode. If the clock card is not in holdover mode, this command is ignored. You cannot force the reference to a port if the clock card is in free-running mode.

Note	This command is not applicable on the SC train.

Note	The clock card enters holdover mode if the forced reference is lost, even if the other external reference is available.

To support the clock feature set in VoIP configurations, a Cisco uBR7246 VXR chassis, equipped with a clock card; and a Cisco uBR-MC16S, a Cisco uBR-MC16E, or a Cisco uBR-MC28C cable interface line card must be used running Cisco IOS Release 12.1(1a)T1 or later releases. Only these cable interface line cards support the external clock card reference from a clock card to distribute that signal to CMs or set-top boxes (STBs) attached to the specific network segments. You can use other cable interface cards, such as the Cisco uBR-MC16C, with the clock card, but these other cable interfaces will not synchronize their downstream SYNC messages with the external clock source.

Each CM or STB must also support VoIP applications and the clock feature set. For example, the Cisco uBR924, running Cisco IOS Release 12.0(7)T or later releases, supports the clock card feature automatically.

Usage Guidelines

Because the clock card automatically provides the timing reference to the midplane TDM clock, the midplane cannot in turn act as the reference for the clock card. This means that the cable clock source-midplane command does not take effect unless a port adapter is configured as the primary clock reference source for the midplane.

Note	This command is not applicable on the SC train.

To support the clock feature set in VoIP configurations, a Cisco uBR7246 VXR chassis, equipped with a clock card; and a Cisco uBR-MC16S, a Cisco uBR-MC16E, or a Cisco uBR-MC28C cable interface line card must be used running Cisco IOS Release 12.1(1a)T1 or higher releases. Only these cable interface line cards support the external clock card reference from a clock card to distribute that signal to CMs or set-top boxes (STBs) attached to the specific network segments. You can use other cable interface cards, such as the Cisco uBR-MC16C, with the clock card, but these other cable interfaces will not synchronize their downstream SYNC messages with the external clock source.

Each CM or STB must also support VoIP applications and the clock feature set. The Cisco uBR924, running Cisco IOS Release 12.0(7)T or later releases, supports the clock card feature automatically.

Usage Guidelines

In Cisco IOS Release 12.2(33) SCC and later, you can manually upgrade the FPGA image only if a single DTCC card is installed on the Cisco uBR 10012 router. If the manual upgrade fails or is interrupted, the DTCC card may become unusable. Do not reset or unplug the DTCC card during the manual upgrade. We recommend that you take precaution against extended downtime if the FPGA upgrade fails unexpectedly by having a standby DTCC card installed on the Cisco uBR10012 router.

Note	You will have to enter y (yes ) when the system prompts you to continue the manual upgrade.

Usage Guidelines

The cable cm-status command updates the event table for the MAC Domain Descriptor (MDD) belonging to a primary channel. The help text of the command provides a mapping of an event type to the corresponding integer.

The ten CM status events are:

1. Secondary channel MDD time-out

2. QAM/FEC lock failure

3. Sequence out-of-range

4. MDD recovery

5. QAM/FEC lock recovery

6. T4 time-out

7. T3 re-tries exceeded

8. Successful ranging after T3 re-tries exceeded

9. CM operating on battery backup

10. CM returned to A/C power

Note

The CM-STATUS message event ‘sequence out of range’ is enabled and supported on the Cisco Wideband SPA from Cisco IOS Release 12.2(33)SCE5 onwards. When the Cisco CMTS receives the ‘sequence out of range’ event, it toggles the sequence-change-count (SCC) bit for each of the indicated downstream service identifiers (DSIDs).

Usage Guidelines

This command applies to all non-primary RF channels on a CMTS.

The ten CM status events per interface on the Cisco uBR10012 and Cisco uBR7200 series routers are:

• 1—Secondary channel MDD time-out

• 2—QAM/FEC lock failure

• 3—Sequence out of range

• 4—MDD recovery

• 5— QAM/FEC lock recovery

• 6—T4 time-out

• 7— T3 re-tries exceeded

• 8— Successful ranging after T3 re-tries exceeded

• 9— CM operating on battery backup

• 10— CM returned to A/C power

The six CM status events per interface on the Cisco cBR series routers are:

• 3—Sequence out of range

• 6—T4 time-out

• 7—T3 re-tries exceeded

• 8— Successful ranging after T3 re-tries exceeded

• 9—CM operating on battery backup

• 10— CM returned to A/C power

Note	If the no form of the command is executed on the interface for specific events, then the show running-config interface command lists the events only that are enabled. If no events are enabled then, the show running interface cable command displays no cable cm-stauts enable with the events.

Usage Guidelines

The cable cmc command configures the resource sharing between the Cisco CMCs in a channel group based on the MAC address.

The valid downstream RF power value is based on the number of active downstream RF channels on the Cisco CMC. If the configured downstream RF power value for a specific number of downstream RF channels is out of the valid range, the downstream RF power is adjusted according to the number of active downstream RF channels on the Cisco CMC and a warning message is displayed.

We recommend that you use the following downstream RF power values based on the number of active downstream RF channels:

Usage Guidelines

Before upgrading the Cisco CMC image through the Cisco CMTS, you must specify the TFTP or FTP server address and the full file path in the DHCP server.

Usage Guidelines

The Cisco CMTS router maintains an internal list of cable modems and CPE devices that were connected on its cable interfaces in the last 24 hours. This list does not capture cable modems and CPE devices that were connected before the last 24 hours.

The CMTS router uses this list to provide the data for various show commands and to respond to SNMP requests that query the entries in the cdxCmCpeTable table in the CISCO-DOCS-EXT-MIB MIB.

By default, the Cisco CMTS router uses the current list if it is less than 3 minutes old. If the current list is older than 3 minutes, the Cisco CMTS router considers it invalid and rebuilds a new list. This prevents the CMTS router from having to build a new list for every query, which could impact system performance.

You can use the cable cmcpe-list valid-time command to change the length of time that the CMTS router considers the current CM and CPE device list to be valid. This allows you to find the optimum time value that provides the most current information without affecting the number of CPU cycles that are available for network processing.

A smaller time period ensures that the CM and CPE device list is more current but it requires more processing time to maintain the list. A longer time period reduces the load on the processor but the CM/CPE list might not be current.

If CPU usage dramatically increases when performing SNMP queries of the cdxCmCpeTable table, use this command to increase the valid list time so that the Cisco CMTS router does not have to rebuild the CM/CPE list more often than needed to respond to the queries.

Note	To find the current valid list time, use the show running-config command and look for the cable cmcpe-list valid-time command in the output. If the command does not appear, the valid list time is set for its default value.

Usage Guidelines

This configuration allows you to define the value for the CMTS ID portion of Gate IDs. The CMTS ID value is the 13 least significant bits (0-12) of the Gate ID.

Usage Guidelines

A DOCSIS CMTS router automatically downloads a DOCSIS configuration file to a CM during its initial registration procedure. The DOCSIS configuration file configures the CM for its network operations and includes information such as the maximum number of CPE devices that are supported, the quality of service (QoS) options provided for the CM, and whether the CM should upgrade to a new software image.

The DOCSIS specification defines the format of the DOCSIS configuration files, which can be created by any number of tools. In addition to the other tools that Cisco provides for this purpose, the cable config-file command can be used to create the DOCSIS configuration files needed for your network. These configuration files are stored in the Flash memory on the Cisco CMTS router and can be automatically downloaded to the CM as needed.

The cable config-file command creates the DOCSIS configuration file if it does not already exist and then enters config-file configuration mode. You can then give one of the following subcommands to create the configuration file:

• access-denied

• channel-id

• cpe max

• download

• frequency

• option

• privacy

• service-class

• snmp manager

• timestamp

Note

When a DOCSIS shared secret is configured on the downstream interface (see the cable shared-secret command ), the cable config-file command automatically inserts the appropriate MD5 Message Integrity Check (MIC) value at the end of the dynamically generated DOCSIS configuration file. You do not need to specify the DOCSIS shared secret string with the cable config-file command.

After using the cable config-file subcommands, enter the exit command to leave config-file mode and to save the configuration file in the Flash memory. After a configuration file is created, it also appears in the running-configuration file. To delete a configuration file and remove it from Flash memory, use the no cable config-file command

To allow CMs to download the configuration files, you must also enable the router’s onboard TFTP server, using the tftp-server configuration command. Unless you are running on a small lab network, you should also remove the default limit of 10 TFTP sessions by using the service udp-small-serves max-servers no limit command.

In addition, the following commands are also recommended:

• cable time-server - Enables the Cisco CMTS router to function as a time-of-day (ToD) server.

• ip dhcp pool - Configures the Cisco CMTS router as a DHCP server. Otherwise, you need an external DHCP server.

• ip dhcp ping packets 0 - Improves the scalability of the Cisco CMTS router DHCP server.

Note	For complete information on DOCSIS configuration files, see Appendix C in the DOCSIS 1.1 Radio Frequency (RF) Interface Specification, available on the DOCSIS Cable Labs official web site at http://www.cablemodem.com

Usage Guidelines

i-CMTS controllers are configured using legacy controller configuration commands by default. If you want to use i-CMTS controller profile, then you must enable it first.