failover between two different routing link

engraed96 · ‎06-11-2007

I?ve main router connected to two remote site each site have dual connection to the main site one connection through IP-VPN (MPLS ) using BGP routing&the other link through lease line using static routing my question is how to configure the main &remote routers for failover in case one of the links goes down

CSCO10892433 · ‎06-11-2007

Hi, engraed96

Two strategies can be implemented

1. Use longest-prefix-match logic. Make your preffered route more specific and the other route less specific. For example, if the destination on the main site is 10.1.1.0/24 and you prefer BGP route , you can make the static route less specfic like this:

ip route 10.1.1.0 255.255.254.0 next-hop-address

By doing so, both BGP and static routes will be install into the routing table. But the BGP route will be used because it has longer prefix mask. Once the BGP route is gone for some reason, the static route will take over.

2. Use shortest Administrative Distance logic. Designate a shorter AD to your preffered route. By default, static route has AD=1 and eBGP route has AD=20, so static route will be installed in the ip routing table and be used to forward packet. If you preffered BGP route, you can designate a longer AD (AD=254, for example)to the static route like this

ip route 10.1.1.0 255.255.255.0 next-hop-address 254

Now the BGP route has shorter AD than the static route and will be installed into the routing table.Once the BGP route is gone for some reason, the static route will take over.

To make sure you have symmetric routing, do the same thing on both main and remote sites.

HTH

SSLIN

Richard Burts · ‎06-11-2007

raed

I would suggest that the first thing to do is to be explicit about what routing behavior you want to achieve. You have indicated that BGP will run over the MPLS VPN. But you have not identified what you plan for the serial. (And of course what to do with the serial depends on what you want the routing behavior to be) If you want the routing behavior to be that the MPLS VPN is the preferred path and the serial is the backup path then there is a simple solution: maintain BGP routing over the MPLS VPN and configure floating static routes specifying the static route and with an administrative distance greater than the AD of BGP.

If you prefer a different routing behavior then it would help us to give you a good answer if you could tell us what you want the routing behavior to be.

HTH

Rick

HTH

Rick

engraed96 · ‎06-12-2007

For both SSLIN &Rick thanks for your suggestion &I?m going to apply it &once it done successfully I?ll inform you

Best regards,

engraed96 · ‎06-12-2007

Hi

By the way ,I will go through the 2nd suggestion to increase the AD for the static router since I prefer BGP over it but I would like to inform you that I have two different IP class for both so is it applicable.?

Richard Burts · ‎06-12-2007

raed

I think that I do not understand well your comment. But increasing the AD to create floating static routes is applicable no matter how many different IP classes you have.

HTH

Rick

HTH

Rick