ISP Redundancy in multihomed BGP scenario

[arumugasamy]

Hi all,

We have setup the WAN network multihomed with dual ISP. The requirement is that if the primary ISP fail then all the traffic should automatically divert to the secondary ISP. How can we achieve it?  If you know that we can use keepalive then could you provide me the configuration with the scenario. In normal working setup, all the traffic for the internal network comes through ISP 1 but if ISP 1 failed then without manual attribute manipulation BGP automatically route the traffic to ISP 2.

Thanks

[Nagendra Kumar Nainar]

Arumugam,

I hope you have BGP session with both ISP. So it should be taken care automatically. You might see some delay in convergence but there is no need for any manual attribute manipulation or intervene to get the traffic redirected to secondary ISP.

Can you share the config you have to make sure if the design is intended to fall back to secondary ISP?.

-Nagendra

[arumugasamy]

Thanks kumar for your quick reply.

Customer says that during isp failure automatic switchover to second isp does not happen and he has to manually do it. I will share the config below.

One more thing that with this config isp 2 router not shows any routes but isp 1 routers only shows all learnt routes.

Thx

[milan.kulik]

Hi,

what exactly does not work during the switchover to the second ISP?

Your router is not getting prefixes from the second ISP or the second ISP is not getting proper prefixes from you?

I believe the second case is happenning?

As I see in the config

ip access-list extended Range-2
permit ip 7.17.24.0 0.0.0.255 any
ip access-list extended Range-3
permit ip 7.17.24.0 0.0.0.255 any

i.e., both ranges are identical, which is not correct, I guess?

And generally, I don't think using extended ACLs in a BGP route-map is a good idea, see

http://blog.ipspace.net/2008/03/use-extended-access-lists-to-filter-bgp.html

It's much easier to understand the config when ip prefix-lists are used instead, I can't follow your current config idea to be honest.

Best regards,

Milan