object tracking ??

Answered Question
Nov 17th, 2007

hi guys, i have router that is connected to 2 ISP's, the link to ISP1 is of 786 and that of ISP2 is 1 mb, due to some constraints we want the link to ISP1 to be primary and ISP2 to be backup, now normally it happens that there is some internal problem in ISP1 and the internet is not working while the interface status remains UP!!, so now we cant easily shift to the other link since the primary link never physically goes down !! to solve this problem i know we can use OER but its posing 2 problems

1) in OER as far as i know we cannot determine our primary link, OER will judge itself which link to use and install static routers for it so we cant define our primary link

2) if any of the participating interface goes down OER doesnt work since atleast 2 interfaces are required for it..

I planned to use object tracking with this in mind

define 2 default routes with the one with ISP with greater AD. now the object will track a particular prefix and in case if its down it will not install the primary default route and hence we will shift to the other route.

now the router is 3845 and rtr commands doesnt work anymore, a guy mentioned SLA but honestly i am not able to put it into work can some1 give me a sample configuration as to how to use it to solve my problem since this a very common issue for any organization, if there is some completely different soultion then kindly tell me

plz remember that i cannot run BGP with any of the ISP they have refused to do it

any ideas ?? kindly help me out

thanks

Correct Answer by azoulflak about 9 years 3 months ago

rtr is replaced by ip sla monitor.

I modified the example found here :http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hirp_c/ch20/h_pbrtrk.htm

----------------

! define and start the SAA operations

!

ip sla monitor 1

type echo protocol ipIcmpEcho 10.1.1.1

ip sla monitor schedule 1 life forever start-time now

!

ip sla monitor 2

type echo protocol ipIcmpEcho 10.2.2.2

ip sla monitor schedule 2 life forever start-time now

!

!track the SAA operations

!

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 alpha

!

! 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 alpha

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

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Correct Answer
azoulflak Sat, 11/17/2007 - 12:46

rtr is replaced by ip sla monitor.

I modified the example found here :http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hirp_c/ch20/h_pbrtrk.htm

----------------

! define and start the SAA operations

!

ip sla monitor 1

type echo protocol ipIcmpEcho 10.1.1.1

ip sla monitor schedule 1 life forever start-time now

!

ip sla monitor 2

type echo protocol ipIcmpEcho 10.2.2.2

ip sla monitor schedule 2 life forever start-time now

!

!track the SAA operations

!

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 alpha

!

! 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 alpha

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

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