Multihoming / Link Redundancy

[netbeginner]

Dear Experts,

Here we stuck up with the network scenerio with some limitations.

We having two routers connected with Two Different ISPs respectivetively...both these routers running with BGP with ISPs. These routers are then connected to same L3 swicth 3700 series for LAN extension. Here we want to make a network where in case of failure of 1st ISP link traffic will auto shift to IInd ISP link and when Ist link restore traffic will be shift back to Ist ISP link.

Limitations :-  here we may use HSRP on routers but the problem is that WAN links are ethernet link, Hence we can't track these WAN interfaces  in HSRP b'coz they will never go down as they are ethernet ports unless & untill someone unplug the cable. If ports not goes down HSRP will not shift the traffic to their backup router.

Pls provide a solution for this scenerio..

****

[Sebastian Fernandez]

Use IP SLA and track the bgp neighor address for tracking

http://www.cisco.com/en/US/docs/ios/12_4/ip_sla/configuration/guide/hsoverv.html

Rgds,

Sebastian

[netbeginner]

Thanks sebastian,

unfortunately i am unable to understand this IP sla.

could u pls share the configs for that.

[mvsheik123]

Hello,

In addition to Sebastian's recomendation, PfR also can be used in this scenario. Edison recomended this link to me as I posted similar queries like yours with hsrp etc.

http://docwiki.cisco.com/wiki/PfR:Home

hth

MS

[Sebastian Fernandez]

Here's a sample

! 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



use these track objects in HSRP configs. As below
int fa 0/0
 standby 1 track 123 decrement 50

IP SLA sends icmp echos to the configured IP (in your case bgp next-hop address) and if the echo fails, track changes it states to down there by reducing HSRP priority for failover.


Please rate post if you find it usefull. 

Rgds,
Sebastian