PBR Support for Multiple Tracking Options

The PBR Support for Multiple Tracking Options feature extends the capabilities of object tracking using Cisco Discovery Protocol (CDP) to allow the policy-based routing (PBR) process to verify object availability by using additional methods. The verification method can be an Internet Control Message Protocol (ICMP) ping, a User Datagram Protocol (UDP) ping, or an HTTP GET request.

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Information About PBR Support for Multiple Tracking Options

Object Tracking

Object tracking is an independent process that monitors objects such as the following:

  • State of the line protocol of an interface

  • Existence of an entry in the routing table

  • Results of a Service Assurance Agent (SAA) operation, such as a ping

Clients such as Hot Standby Router Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), Gateway Load Balancing Protocol (GLBP), and (with this feature) PBR can register their interest in specific, tracked objects and then take action when the state of the objects changes.

PBR Support for Multiple Tracking Options Feature Design

The PBR Support for Multiple Tracking Options feature gives PBR access to all the objects that are available through the tracking process. The tracking process provides the ability to track individual objects--such as ICMP ping reachability, routing adjacency, an application running on a remote device, a route in the Routing Information Base (RIB)--or to track the state of an interface line protocol.

Object tracking functions in the following manner. PBR will inform the tracking process that a certain object should be tracked. The tracking process will in turn notify PBR when the state of that object changes.

How to Configure PBR Support for Multiple Tracking Options

The tasks in this section are divided according to the Cisco IOS release that you are running because Cisco IOS Release 12.3(14)T introduced new syntax for IP Service Level Agreements (SLAs). To use this feature, you must be running Cisco IOS Release 12.3(4)T, 12.2(25)S, or a later release. This section contains the following tasks:

Configuring PBR Support for Multiple Tracking Options

Perform this task to configure PBR support for multiple tracking options. In this task, a route map is created and configured to verify the reachability of the tracked object.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ip sla monitor operation-number
  4. type echo protocol ipIcmpEcho {destination-ip-address | destination-hostname } [source-ipaddr {ip-address | hostname } | source-interface interface-name ]
  5. exit
  6. ip sla monitor schedule operation-number [life {forever | seconds }] [start-time {hh : mm [: ss ] [month day | day month ] | pending | now | after hh : mm : ss }] [ageout seconds ] [recurring ]
  7. track object-number rtr entry-number [reachability | state ]
  8. delay {up seconds [down seconds ] | [up seconds ] down seconds }
  9. exit
  10. interface type number
  11. ip address ip-address mask [secondary ]
  12. ip policy route-map map-tag
  13. exit
  14. route-map map-tag [permit | deny ] [sequence-number ] [
  15. set ip next-hop verify-availability [next-hop-address sequence track object ]
  16. end
  17. show track object-number
  18. show route-map [map-name | all | dynamic ]

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

ip sla monitor operation-number

Example:


Device(config)# ip sla monitor 1

Starts a Cisco IOS IP Service Level Agreement (SLA) operation configuration and enters IP SLA monitor configuration mode.

Step 4

type echo protocol ipIcmpEcho {destination-ip-address | destination-hostname } [source-ipaddr {ip-address | hostname } | source-interface interface-name ]

Example:


Device(config-sla-monitor)# type echo protocol ipIcmpEcho 10.1.1.1

Configures an IP SLA Internet Control Message Protocol (ICMP) echo probe operation.

Step 5

exit

Example:


Device(config-sla-monitor)# exit

Exits IP SLA monitor configuration mode and returns the device to global configuration mode.

Step 6

ip sla monitor schedule operation-number [life {forever | seconds }] [start-time {hh : mm [: ss ] [month day | day month ] | pending | now | after hh : mm : ss }] [ageout seconds ] [recurring ]

Example:


Device(config)# ip sla monitor schedule 1 life forever start-time now

Configures the scheduling parameters for a single Cisco IOS IP SLA operation.

  • In this example, the time parameters for the IP SLA operation are configured.

Step 7

track object-number rtr entry-number [reachability | state ]

Example:


Device(config)# track 123 rtr 1 reachability

Tracks the reachability of a Response Time Reporter (RTR) object and enters tracking configuration mode.

Step 8

delay {up seconds [down seconds ] | [up seconds ] down seconds }

Example:


Device(config-track)# delay up 60 down 30

(Optional) Specifies a period of time, in seconds, to delay communicating state changes of a tracked object.

Step 9

exit

Example:


Device(config-track)# exit

Exits tracking configuration mode and returns the device to global configuration mode.

Step 10

interface type number

Example:


Device(config)# interface serial 2/0

Specifies an interface type and number and enters interface configuration mode.

Step 11

ip address ip-address mask [secondary ]

Example:


Device(config-if)# ip address 192.168.1.1 255.255.255.0

Specifies a primary or secondary IP address for an interface.

  • See the "Configuring IPv4 Addresses" chapter of the Cisco IOS IP Addressing Services Configuration Guide for information on configuring IPv4 addresses.

  • In this example, the IP address of the incoming interface is specified. This is the interface on which policy routing is to be enabled.

Step 12

ip policy route-map map-tag

Example:


Device(config-if)# ip policy route-map alpha

Enables policy routing and identifies a route map to be used for policy routing.

Step 13

exit

Example:


Device(config-if)# exit

Exits interface configuration mode and returns the device to global configuration mode.

Step 14

route-map map-tag [permit | deny ] [sequence-number ] [

Example:


Device(config)# route-map alpha permit ordering-seq

Configures a route map and specifies how the packets are to be distributed.

Step 15

set ip next-hop verify-availability [next-hop-address sequence track object ]

Example:


Device(config-route-map)# set ip next-hop verify-availability 10.1.1.1 10 track 123

Configures the route map to verify the reachability of the tracked object.

  • In this example, the policy is configured to forward packets received on serial interface 2/0 to 10.1.1.1 if that device is reachable.

Step 16

end

Example:


Device(config-route-map)# end

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

Step 17

show track object-number

Example:


Device# show track 123

(Optional) Displays tracking information.

  • Use this command to verify the configuration. See the display output in the "Examples" section of this task.

Step 18

show route-map [map-name | all | dynamic ]

Example:


Device# show route-map alpha

(Optional) Displays route map information.

  • In this example, information about the route map named alpha is displayed. See the display output in the "Examples" section of this task.

Examples

The following output from the show track command shows that the tracked object 123 is reachable. 


Device# show track 123
Track 123
  Response Time Reporter 1 reachability
  Reachability is Up
    2 changes, last change 00:00:33
  Delay up 60 secs, down 30 secs
  Latest operation return code: OK
  Latest RTT (millisecs) 20
  Tracked by:
    ROUTE-MAP 0

The following output from the show route-map command shows information about the route map named alpha that was configured in the task. 


Device# show route-map alpha
route-map alpha, permit, sequence 10
  Match clauses:
  Set clauses:
    ip next-hop verify-availability 10.1.1.1 10 track 123  [up]
  Policy routing matches: 0 packets, 0 bytes

Configuration Examples for PBR Support for Multiple Tracking Options

Example: Configuring PBR Support for Multiple Tracking Options

The following example shows how to configure PBR support for multiple tracking options.

The configured policy is that packets received on Ethernet interface 0, should be forwarded to 10.1.1.1 only if that device is reachable (responding to pings). If 10.1.1.1 is not up, then the packets should be forwarded to 10.2.2.2. If 10.2.2.2 is also not reachable, then the policy routing fails and the packets are routed according to the routing table.

Two RTRs are configured to ping the remote devices. The RTRs are then tracked. Policy routing will monitor the state of the tracked RTRs and make forwarding decisions based on their state. 


! Define and start the RTRs.
ip sla monitor 1
 type echo protocol ipicmpecho 10.1.1.1
ip sla monitor schedule 1 start-time now life forever
!
ip sla monitor 2
 type echo protocol ipicmpecho 10.2.2.2
ip sla monitor schedule 2 start-time now life forever
!
! Track the RTRs.
track 123 rtr 1 reachability
track 124 rtr 2 reachability
!
! Enable policy routing on the incoming interface.
interface ethernet 0
 ip address 10.4.4.4 255.255.255.0
 ip policy route-map beta
!
! 10.1.1.1 is via this interface.
interface ethernet 1
 ip address 10.1.1.254 255.255.255.0
!
! 10.2.2.2 is via this interface.
interface ethernet 2
 ip address 10.2.2.254 255.255.255.0
!
! Define a route map to set the next-hop depending on the state of the tracked RTRs.
route-map beta
 set ip next-hop verify-availability 10.1.1.1 10 track 123
 set ip next-hop verify-availability 10.2.2.2 20 track 124

Additional References

The following sections provide references related to the PBR Support for Multiple Tracking Options feature.

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Command List, All Releases

Object tracking within Cisco IOS software

Configuring Enhanced Object Tracking" chapter of the Cisco IOS IP Application Services Configuration Guide

Configuring IP addresses

"Configuring IPv4 Addresses" chapter of the Cisco IOS IP Addressing Services Configuration Guide

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Feature Information for PBR Support for Multiple Tracking Options

The following table provides release information about the feature or features described in this module. This table 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.

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.
Table 1. Feature Information for PBR Support for Multiple Tracking Options

Feature Name

Releases

Feature Information

PBR Support for Multiple Tracking Options

12.3(4)T

The PBR Support for Multiple Tracking Options feature extends the capabilities of object tracking using Cisco Discovery Protocol (CDP) to allow the policy-based routing (PBR) process to verify object availability by using additional methods. The verification method can be an Internet Control Message Protocol (ICMP) ping, a User Datagram Protocol (UDP) ping, or an HTTP GET request.

The following commands were introduced or modified by this feature: set ip next-hop verify-availability .