Cisco CMTS Router Layer 2 and VPN Features Configuration Guide, Release 12.2SC - VRF Steering for Cisco CMTS Routers [Support]

Table Of Contents

VRF Steering for Cisco CMTS Routers

Finding Feature Information

Contents

Prerequisites for VRF Steering

Restrictions for VRF Steering

Information About VRF Steering

VRF Steering Process

How to Configure VRF Steering

Configuring the VRF Steering

Troubleshooting Tips

Configuration Examples for VRF Steering

Example: VRF Steering for CMTS Routers

Verifying VRF Steering

Verifying VRF Steering

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for VRF Steering

VRF Steering for Cisco CMTS Routers

First Published: June 20, 2011

The virtual routing and forwarding (VRF) steering feature allows provisioning of data traffic from cable modems to be contained to a specified VRF instance. This enables all traffic from and to a particular set of cable modems to be constrained to a VRF instance.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for VRF Steering" section.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for VRF Steering

•Restrictions for VRF Steering

•Information About VRF Steering

•How to Configure VRF Steering

•Configuration Examples for VRF Steering

•Verifying VRF Steering

•Additional References

•Feature Information for VRF Steering

Prerequisites for VRF Steering

Table 1 shows the hardware compatibility prerequisites for this feature.

Note The hardware components introduced in a given Cisco IOS Release are supported in all subsequent releases unless otherwise specified.

Table 1 Cable Hardware Compatibility Matrix for VRF Steering

Platform

Processor Engine

Cable Interface Cards

Cisco uBR10012 Universal Broadband Router

Cisco IOS Release 12.2(33)SCF and later releases

•PRE2

•PRE4

Cisco IOS Release 12.2(33)SCF and later releases

•Cisco uBR10-MC5X20H

•Cisco UBR-MC20X20V

•Cisco uBR-MC3GX60V¹

Cisco uBR7246VXR Universal Broadband Router

Cisco IOS Release 12.2(33)SCF and later releases

•NPE-G1

•NPE-G2

Cisco IOS Release 12.2(33)SCF and later releases

•Cisco uBR-MC28U/X

•Cisco uBR-MC88V

Cisco uBR7225VXR Universal Broadband Router

Cisco IOS Release 12.2(33)SCF and later releases

•NPE-G1

•NPE-G2

Cisco IOS Release 12.2(33)SCF and later releases

•Cisco uBR-MC28U/X

•Cisco uBR-MC88V

¹The Cisco uBR-MC3GX60V line card is supported only with PRE4.

Restrictions for VRF Steering

•Customer premise equipment (CPE) cannot specify a VRF instance unlike the cable modem.

•Only a single instance of the cable vrf-steering cable-modem command is supported.

•Only IPv4 is supported.

Information About VRF Steering

The VRF steering feature is developed to address the need for accommodating more IPv4 addresses when customers run out of IPv4 addresses for their CPE. This solution helps customers expand their existing IP address space until they move to the IPv6 address mode.

The availability of new IPv4 addresses is quickly coming to an end. In order to continue provisioning new subscribers, operators must switch to IPv6. This feature is designed to give the operators additional time to switch to IPv6 by expanding the use of non-traditional IPv4 addresses within their network. This feature allows the operator to create a private VRF for cable modems that are not routable outside of the operator network and choose any address since the CM addresses will not be routed externally. The CPE devices will continue to be provisioned with globally routable addresses, allowing them to peruse the internet.

VRF Steering Process

Figure 1 and the following sequence of events describe the VRF steering process.

Figure 1 VRF Steering Process

1. The master bundle interface has at least 2 sub-bundles configured. The CPE is routed using the global sub-bundle interface. The CM is routed using the private VRF sub-bundle interface.

2. CM address negotiation happens using helper-address of the private VRF sub-bundle interface.

3. CPE address negotiation happens using helper-address of the global sub-bundle interface.

4. The Cisco CMTS steers all cable modem data traffic into the VRF. CM traffic that is punted to the route processor (RP) is forwarded only on the CM VRF.

5. At this point the CPE is able to get an IP address using the global Dynamic Host Configuration Protocol (DHCP) server. Since the CPE traffic is not classified, it uses the global routing table and is routable.

How to Configure VRF Steering

•Configuring the VRF Steering (required)

Configuring the VRF Steering

This section describes how to configure a VRF instance on the Cisco CMTS router.

SUMMARY STEPS

Create a private routing table for the CMs.

1. enable

2. configure terminal

3. ip vrf vrf-name

Create an ACL and route-map to match the CPE traffic and to steer the CPE traffic to the global subinterface from the CM subinterface. The route map needs to reference the ACL. Steps 4 and 5 are applicable to Cisco uBR10012 routers only.

4. ip access-list extended access-list name

5. route-map map-tag permit sequence number

Create the master bundle interface and add the new command to steer the CMs into the appropriate subinterface.

6. interface bundle n

7. cable vrf-steering cable-modem vrf-name

Create the subinterface for the CPEs.

8. interface bundle n1

9. ip address ip-address mask secondary

10. cable dhcp-giaddr policy

11. cable helper-address IP-address

12. exit

Create the subinterface for the CMs.

13. interface bundle n2

14. ip vrf forwarding vrf-name

15. ip address ip-address mask

16. ip policy route-map map-tag

17. cable helper-address IP-address

18. cable source-route

19. exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable
Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 3

ip vrf vrf-name
Example:

Router(config)# ip vrf CM-VRF
rd 100:100
route-target export 100:100
route-target import 100:100

Defines a VRF instance and enters the interface configuration mode.

•vrf-name—Name assigned to a VRF.

Step 4

ip access-list extended access-list-name
Example:

Router(config)# ip access-list extended vrfcpe
permit ip 111.1.0.0 0.0.255.255 any
permit ip 112.1.0.0 0.0.255.255 any
permit ip 101.1.0.0 0.0.255.255 any

Specifies an extended IP access list to enable filtering for packets with IP helper-address destinations.

•access-list-name—Name of the IP access list or object-group ACL. Names cannot contain a space or quotation mark, and must begin with an alphabetic character to prevent ambiguity with numbered access lists.

Step 5

route-map map-tag permit sequence-number
Example:

Router(config)# route-map cpe permit 10
Router(config)#route-map cpe permit 10
Router(config-route-map)# match ip address vrfcpe
Router(config-route-map)# set global

Defines the conditions for redistributing routes from one routing protocol into another routing protocol, or to enable policy routing. The route map needs to reference the ACL.

•map-tag—A meaningful name for the route map.

•sequence-number—Number that indicates the position a new route map will have in the list of route maps already configured with the same name.

Step 6

interface bundle n
Example:

Router(config-if)# interface Bundle1

Adds the selected interface to the virtual bundle. If this is the first interface on which the virtual bundle is configured, this command enables the bundle on the specified interface.

•n—Interface bundle number. You can configure as many as 40 virtual interface bundles on the Cisco CMTS. The numeric identifiers may range from 1 to 255.

Step 7

cable vrf-steering cable-modem vrf-name
Example:

Router(config-if)# cable vrf-steering cable-modem CM-VRF

Steers or directs cable modems to the specified VRF in the cable interface configuration mode.

•vrf-name—The VPN Routing/ Forwarding instance name.

Step 8

interface bundle n.1
Example:

Router(config-if)# interface Bundle1.1

Adds the selected interface to the virtual bundle. If this is the first interface on which the virtual bundle is configured, this command enables the bundle on the specified interface.

•n.1—Interface sub-bundle number. You can configure as many as 40 virtual interface bundles on the Cisco CMTS. Numeric identifiers may range from 1 to 255.

Step 9

ip address ip-address mask secondary
Example:

Router(config-subif)# ip address 112.1.1.1 255.255.0.0 secondary

Sets a secondary IP address for an interface.

Note Create a primary interface address before setting a secondary IP address. If the secondary address is used for a VRF table configuration with the vrf keyword, the vrf keyword must be specified also.

Step 10

cable dhcp-giaddr policy
Example:

Router(config-subif)# cable dhcp-giaddr policy

(Optional) Selects the control policy, so that the primary address is used for cable modems and the secondary addresses are used for hosts and other CPE devices.

Step 11

cable helper-address IP-address
Example:

Router(config-subif)# cable helper-address 72.10.10.2

Specifies a destination IP address for User Datagram Protocol (UDP) broadcast DHCP packets in cable subinterface configuration mode.

•IP-address—The IP address of a DHCP server to which UDP broadcast packets will be sent.

Step 12

exit
Example:

Router(config-subif)# end

Exits the subinterface configuration mode.

Step 13

interface bundle n.2
Example:

Router(config-if)# interface Bundle1.2

Adds the selected interface to the virtual sub-bundle. If this is the first interface on which the virtual bundle is configured, this command enables the bundle on the specified interface.

•n.2—Interface sub-bundle number. You can configure as many as 40 virtual interface bundles on the Cisco CMTS. Numeric identifiers may range from 1 to 255.

Step 14

ip vrf forwarding vrf-name
Example:

Router(config-subif)# ip vrf forwarding CM-VRF

Associates a VRF instance with an interface or subinterface.

•vrf-name—Name assigned to a VRF.

Step 15

ip address ip-address mask
Example:

Router(config-subif)# ip address 72.10.10.1 255.255.0.0

Sets a primary or secondary IP address for the specified interface.

•mask—Mask for the associated IP subnet address.

Step 16

ip policy route-map map-tag
Example:

Router(config-subif)# ip policy route-map cpe

Identifies a route map to use for policy routing on an interface.

•map-tag—Name of the route map to use for policy routing. The name must match a map-tag value specified by a route-map command.

Step 17

cable helper-address IP-address
Example:

Router(config-subif)# cable helper-address 72.10.10.2

Specifies a destination IP address for User Datagram Protocol (UDP) broadcast Dynamic Host Configuration Protocol (DHCP) packets in cable subinterface configuration mode.

•IP-address—The IP address of a DHCP server to which UDP broadcast packets will be sent.

Step 18

cable source-route
Example:

Router(config-subif)# cable source-route

Configures the VRF source route in the cable modem's sub- bundle interface configuration mode.

Note This command is applicable to Cisco uBR10012 routers only.

Step 19

exit
Example:

Router(config-subif)# exit

Exits the subinterface configuration mode.

Troubleshooting Tips

Run the debug cable bundle vrf-steering command to display the interfaces selected during the configuration.

Configuration Examples for VRF Steering

This section provides the following configuration examples:

•Example: VRF Steering for CMTS Routers

Example: VRF Steering for CMTS Routers

The following example shows how to configure VRF steering on CMTS routers:
Router> enable configure terminal
ip vrf CM-VRF
rd 100:100
route-target export 100:100
route-target import 100:100
! These commands apply to all the devices attached on this cable bundle.
!
interface Bundle1
 no ip address
 no cable arp filter request-send
 no cable arp filter reply-accept
 cable vrf-steering cable-modem CM-VRF
end
!Subinterface for CPEs. 
!
interface Bundle1.1                  
 ip address 112.1.1.1 255.255.0.0 secondary
 ip address 111.1.1.1 255.255.0.0 secondary
 ip address 101.1.1.1 255.255.0.0
 cable dhcp-giaddr policy
 cable helper-address 72.10.10.2
! Subinterface for CMs. These CMs go into CM-VRF
!
interface Bundle1.2
 ip vrf forwarding CM-VRF          
 ip address 72.10.10.1 255.255.0.0
 ip policy route-map cpe
 cable helper-address 72.10.10.2
 cable source-route 
end
! Create ACL for CPE
!
ip access-list extended vrfcpe
 permit ip 111.1.0.0 0.0.255.255 any
 permit ip 112.1.0.0 0.0.255.255 any
 permit ip 101.1.0.0 0.0.255.255 any
! 
! Create route-map for CPE
!
route-map cpe permit 10
 match ip address vrfcpe
end.
Verifying VRF Steering

This section explains how to verify VRF steering configuration for the CMTS router, and it contains the following topics:

•Verifying VRF Steering

Verifying VRF Steering

To verify or view which VRF contains a specific cable modem in the ARP cache table, use the show ip arp vrf command in privileged EXEC mode.

The following is sample output from the show ip arp vrf command:
Router # show ip arp vrf CM-VRF 
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  203.0.113.1                0   0018.742c.6e00  ARPA   FastEthernet0/0/0
Internet  203.0.113.2                -   0014.f1e4.fb58  ARPA   FastEthernet0/0/0
Internet  198.51.100.1               -   0014.f1e4.fc31  ARPA   Bundle1.2
Internet  198.51.100.2               0   001e.6bfb.34e8  ARPA   Bundle1.2
Internet  198.51.100.3               0   0007.0e07.9f1f  ARPA   Bundle1.2
Internet  198.51.100.5               0   0025.2eaf.6bea  ARPA   Bundle1.2
Internet  198.51.100.6               0   001a.c3ff.d1a4  ARPA   Bundle1.2
Internet  198.51.100.7               0   001e.6bfb.1c7e  ARPA   Bundle1.2
Additional References

The following sections provide references related to the VRF Steering feature.

Related Documents

Related Topic

Document Title

Cisco uBR10012 Universal Broadband Router Documentation

IPv6 on Cable

http://www.cisco.com/en/US/docs/ios/cable/configuration/guide/
cmts_ipv6.html

Virtual Interface Bundling for the Cisco CMTS

http://www.cisco.com/en/US/docs/ios/cable/configuration/guide/
cmts_cbl_if_bundlg.html

Cisco uBR10012 Universal Broadband Router Hardware Installation Guide

http://www.cisco.com/en/US/docs/cable/cmts/ubr10012/
installation/guide/hig.html

Cisco uBR10012 Universal Broadband Router Software Configuration Guide http://www.cisco.com/en/US/docs/cable/cmts/ubr10012/
configuration/guide/scg.html

Cisco uBR10012 Universal Broadband Router Release Notes

http://www.cisco.com/en/US/products/hw/cable/ps2209/
prod_release_notes_list.html

CMTS Command Reference

Cisco IOS CMTS Cable Command Reference

http://www.cisco.com/en/US/docs/ios/cable/command/reference/
cbl_book.html

Standards

Standard

Title

None

MIBs

MIB

MIBs Link

None

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

None

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for VRF Steering

Table 2 lists the features in this module and provides links to specific configuration information.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 2 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Table 2 Feature Information for VRF Steering

Feature Name

Releases

Feature Information

VRF Steering

12.2(33)SCF

The VRF steering feature allows provisioning of data traffic from cable modems to be contained to a specified VRF instance.

In Cisco IOS Release 12.2(33)SCF, this feature was introduced on the Cisco CMTS routers.

The following commands were introduced or modified:

•cable source-route

•cable vrf-steering cable-modem

•ip vrf

•show ip arp vrf

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2011 Cisco Systems, Inc. All rights reserved.