PBR Recursive Next Hop

The PBR Recursive Next Hop feature enhances route maps to enable configuration of a recursive next-hop IP address that is used by policy-based routing (PBR). The recursive next-hop IP address is installed in the routing table and can be a subnet that is not directly connected. If the recursive next-hop IP address is not available, packets are routed using a default route.

Because Cisco Express Forwarding (CEF) or process switching provides the infrastructure, the benefit of this feature is the CEF loadsharing.

Feature History for the PBR Recursive Next Hop Feature

Release

Modification

12.0(28)S

This feature was introduced.

12.3(14)T

This feature was integrated into Cisco IOS Release 12.3(14)T.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 table at the end of this module.

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

How to Configure PBR Recursive Next Hop

Setting the Recursive Next-Hop IP Address

The infrastructure provided by CEF or process switching performs the recursion to the next-hop IP address. The configuration sequence, which affects routing, is as follows:

  1. Next-hop

  2. Next-hop recursive

  3. Interface

  4. Default next-hop

  5. Default interface

If both a next-hop and a recursive next-hop IP address are present in the same route-map entry, the next-hop is used. If the next-hop is not available, the recursive next-hop is used. If the recursive next-hop is not available and no other IP address is present, the packet is routed using the default routing table; it is not dropped. If the packet is supposed to be dropped, use the set ip next-hop command with the recursive keyword followed by a set interface null0 configuration.


Note

Match interface is not supported on Cisco Catalyst 3750 series devices.

Perform this task to set the IP address for the recursive next-hop router.

Before you begin

If loadsharing is required, CEF loadsharing should be configured for per-packet or per-destination loadsharing. Loadbalancing should be done over all equal-cost routes to the subnet that have been configured by the set ip next-hop recursive command.

This functionality should be available in centralized and distributed systems.


Note

Only one recursive next-hop IP address is supported per route-map entry.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. access-list permit source
  4. route-map map-tag
  5. set ip next-hop ip-address
  6. set ip next-hop {ip-address [...ip-address ] | recursive ip-address}
  7. match ip address access-list-number
  8. end

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

access-list permit source

Example:


Router(config)# access-list 101 permit 10.60.0.0 0.0.255.255

Configures an access list. The example configuration permits any source IP address that falls within the 10.60.0.0. 0.0.255.255 subnet.

Step 4

route-map map-tag

Example:


Router(config)# route-map abccomp

Enables policy routing and enters route-map configuration mode.

Step 5

set ip next-hop ip-address

Example:


Router(config-route-map)# set ip next-hop 10.10.1.1

Sets a next-hop router IP address.

Note 

Set this IP address separately from the next-hop recursive router configuration.

Step 6

set ip next-hop {ip-address [...ip-address ] | recursive ip-address}

Example:


Router(config-route-map)# set ip next-hop recursive 10.20.3.3

Sets a recursive next-hop IP address.

Note 

This configuration does not ensure that packets get routed using the recursive IP address if an intermediate IP address is a shorter route to the destination.

Step 7

match ip address access-list-number

Example:


Router(config-route-map)# match ip address 101

Sets an access list to be matched.

Step 8

end

Example:


Router(config-route-map)# end

Exits route-map configuration mode and returns to privileged EXEC mode.

Verifying the Recursive Next-Hop Configuration

To verify the recursive next-hop configuration, perform the following steps.

SUMMARY STEPS

  1. show running-config | begin abccomp
  2. show route-map map-name

DETAILED STEPS

Step 1

show running-config | begin abccomp

Use this command to verify the IP addresses for a next-hop and recursive next-hop IP address, for example:

Example:


Router# show running-config
 | begin abccomp
route-map abccomp permit 10
 match ip address 101 ! Defines the match criteria for an access list.
 set ip next-hop recursive 10.3.3.3 ! If the match criteria are met, the recursive IP  address is set.
 set ip next-hop 10.1.1.1 10.2.2.2 10.4.4.4
Step 2

show route-map map-name

Use this command to display the route maps, for example:

Example:


Router# show route-map abccomp
route-map abccomp, permit, sequence 10
 Match clauses:
  ip address (access-lists): 101 
 Set clauses:
  ip next-hop recursive 10.3.3.3
  ip next-hop 10.1.1.1 10.2.2.2 10.4.4.4
 Policy routing matches: 0 packets, 0 bytes

Configuration Examples for PBR Recursive Next Hop

Example: Recursive Next-Hop IP Address

The following example shows the configuration of IP address 10.3.3.3 as the recursive next-hop router: 


route-map abccomp
 set ip next-hop 10.1.1.1
 set ip next-hop 10.2.2.2
 set ip next-hop recursive 10.3.3.3
 set ip next-hop 10.4.4.4

The following example shows the configuration of IPv6 address 2001:DB8:2003:1::95 as the recursive next-hop router: 


route-map abccomp
 set ipv6 next-hop 2001:DB8:2003:1::95
 set ipv6 next-hop 2001:DB8:2004:3::96
 set ipv6 next-hop recursive 2001:DB8:2005:2::95
 set ipv6 next-hop 2001:DB8:2006:1::95

Additional References

The following sections provide references related to the PBR Recursive Next Hop feature.

Related Documents

Related Topic

Document Title

IP routing commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples

Cisco IOS IP Routing Protocols Command Reference

MIBs

MIBs

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

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

Technical Assistance

Description

Link

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To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS IP Routing: Protocol-Independent Command Reference. For information about all Cisco IOS commands, use the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or the Cisco IOS Master Command List, All Releases, at http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html.

  • set ip next-hop

  • show route-map