Configuring IP SLA PBR Object Tracking

This chapter describes the PBR object tracking capabilities of IP Service Level Agreements (SLAs).

This chapter includes the following sections:

IP SLA PBR Object Tracking

This feature allows you to make sure that the next hop is reachable before that route is used. If the next hop is not reachable, another route is used as defined in the policy-based routing (PBR) configuration. If no other route is present in the route map, the routing table is used.

Object Tracking

Object tracking monitors objects such as the following:

  • State of the line protocol of an interface

  • Existence of an entry in the routing table

Clients, such as PBR, can register their interest in specific, tracked objects and then take action when the state of the objects changes.

IP SLA PBR Object Tracking Overview

The PBR Object Tracking feature gives policy-based routing (PBR) access to all the objects that are available through the tracking process. The tracking process enables you 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 informs the tracking process that a certain object should be tracked, and the tracking process then notifies PBR when the state of that object changes.

Configuring IP SLA PBR Object Tracking

Procedure
     Command or ActionPurpose
    Step 1 configure terminal


    Example: 
    switch# configure terminal
     

    Enters global configuration mode.

     
    Step 2 ip sla operation-number


    Example: 
    switch(config)# ip sla 1
     

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

     
    Step 3 icmp-echo destination-ip-address


    Example: 
    switch(config-ip-sla)# icmp-echo 10.3.3.2
     

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

     
    Step 4 exit


    Example: 
    switch(config-ip-sla)# exit
     

    Exits IP SLA configuration mode and returns the router to global configuration mode.

     
    Step 5 ip sla schedule operation-number life forever start-time now


    Example: 
    switch(config)# ip sla 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.

    Note   

    Repeat Steps 2 to 5 to configure and schedule other IP SLA operations.

     
    Step 6 track object-number ip sla entry-number reachability


    Example: 
    switch(config)# track 1 ip sla 1 reachability
     

    Tracks the reachability of an object and enters tracking configuration mode.

    Note   

    Repeat this step to track other operations.

     
    Step 7 exit


    Example: 
    switch(config-track)# exit
     

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

     
    Step 8 ip access-list standard access-list-name


    Example: 
    switch(config)# ip access-list standard ACL
     

    Defines an IP access list access control list (ACL) in order to enable filtering for packets.

     
    Step 9 permit ip source destination


    Example: 
    
switch(config-acl)# permit ip 192.0.2.0/24 198.51.100.0/24
     

    Creates an access control list (ACL) rule that permits traffic matching its conditions.

     
    Step 10 ipv6 access-list access-list-name


    Example: 
    switch(config)# ipv6 access-list IPv6ACL
     

    Defines an IPv6 access list ACL in order to enable filtering for packets.

     
    Step 11 permit ipv6 source destination


    Example: 
    
switch(config-ipv6-acl)# permit ipv6 2001:DB8::/32 2001:DB8::/48
     

    Creates an access control list (ACL) rule that permits traffic matching its conditions.

     
    Step 12 exit


    Example: 
    switch(config-ipv6-acl)# exit
     

    Exits ACL configuration mode and returns the router to global configuration mode.

     
    Step 13 route-map map-tag


    Example: 
    switch(config)# route-map PBR
     

    Specifies a route map and enters route-map configuration mode.

     
    Step 14 match ip address access-list-name


    Example: 
    switch(config-route-map)# match ip address ACL
     

    Distributes any routes that have a destination IPv4 network number address that is permitted by a standard access list.

     
    Step 15 match ipv6 address access-list-name


    Example: 
    switch(config-route-map)# match ipv6 address IPv6ACL
     

    Distributes any routes that have a destination IPv6 network number address that is permitted by a standard access list.

     
    Step 16 set ip next-hop verify-availability next-hop-address track object


    Example: 
    switch(config-route-map)# set ip next-hop verify-availability 198.51.100.2 track 1
     

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

    Note   

    Repeat this step to configure the route map to verify the reachability of other tracked objects.

     
    Step 17 set ipv6 next-hop verify-availability next-hop-address track object


    Example: 
    switch(config-route-map)# set ipv6 next-hop verify-availability 2001:DB8:1::1 track 1
     

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

    Note   

    Repeat this step to configure the route map to verify the reachability of other tracked objects.

     
    Step 18 set ip default next-hop verify-availability next-hop-address track object


    Example: 
    switch(config-route-map)# set ip default next-hop verify-availability 192.0.2.2 track 1
     

    Configures the route map to verify the reachability of the default next hop.

     
    Step 19 set ipv6 default next-hop verify-availability next-hop-address track object


    Example: 
    switch(config-route-map)# set ipv6 default next-hop verify-availability 2001:DB8:0:ABCD::1 track 1
     

    Configures the route map to verify the reachability of the default next hop.

     
    Step 20 exit


    Example: 
    switch(config-route-map)# exit
     

    Exits route-map configuration mode and returns the router to global configuration mode.

     
    Step 21 interface type number


    Example: 
    switch(config)# interface ethernet 0/0
     

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

     
    Step 22 ip address ip-address mask


    Example: 
    switch(config-if)# ip address 10.2.2.1 255.255.255.0
     

    Specifies a primary IP address for an interface.

     
    Step 23 ipv6 address ip-address mask


    Example: 
    switch(config-if)# ipv6 address 2001:DB8::/48
     

    Specifies a primary IPv6 address for an interface.

     
    Step 24 ip policy route-map map-tag


    Example: 
    switch(config-if)# ip policy route-map PBR
     

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

     
    Step 25 ipv6 policy route-map map-tag


    Example: 
    switch(config-if)# ipv6 policy route-map PBR
     

    Enables IPv6 policy routing and identifies a route map to be used for policy routing.

     
    Step 26 end


    Example: 
    switch(config-if)# end
     

    Exits interface configuration mode and returns the router to privileged EXEC mode.

     
    Step 27 show track object-number


    Example: 
    switch# show track 1
     

    (Optional) Displays tracking information.

    Use this command to verify the configuration.

     
    Step 28 show route-map map-name


    Example: 
    switch# show route-map PBR
     

    (Optional) Displays route map information.

     

    Example: Configuring IP SLA PBR Object Tracking

    This example shows that object tracking is configured for PBR: 

    ! Configure and schedule IP SLA operations
ip sla 1
 icmp-echo 10.3.3.2
ip sla schedule 1 life forever start-time now
!
ip sla 2
 udp-echo 10.4.4.2
ip sla schedule 2 life forever start-time now
!
ip sla 3
 icmp-echo 10.5.5.2
ip sla schedule 3 life forever start-time now
!
ip sla 4
 icmp-echo 10.6.6.2
ip sla schedule 4 life forever start-time now
!
ip sla 5
 icmp-echo 10.7.7.2
ip sla schedule 5 life forever start-time now
!
! Configure Object Tracking to track the operations 
!
track 1 ip sla 1 reachability
track 2 ip sla 2 reachability
track 3 ip sla 3 reachability
track 4 ip sla 4 reachability
track 5 ip sla 5 reachability
!
! Configure ACL
ip access-list standard ACL
	permit ip 10.2.2.0/24 10.1.1.1/32
!
! Configure PBR policing on the router
route-map PBR
	match ip address ACL
	set ip next-hop verify-availability 10.3.3.2 track 1
	set ip next-hop verify-availability 10.4.4.2 track 2
	set ip next-hop verify-availability 10.5.5.2 track 3
!
! Apply PBR policy on the incoming interface of the router.
interface ethernet 0/0
 ip address 10.2.2.1 255.255.255.0
 	ip policy route-map PBR
!
! Display PBR related information 
show route-map
show track brief
show ip sla stat
show ip sla application
!