EIGRP and BGP in Multi-Homing

[Vinayaka Raman]

Friends,

Topology:

********

         Remote site

                /

              /

MPLS Service Provider

       /                  \ 

     /                      \

Router A----------Router B

Existing model:

************

Router A and B peers with MPLS service Provider via eBGP..Both local AS numbers and remote AS numbers are same. The service provider does AS over ride

Router A and B peers via P2P link through EIGRP.. (conenct through serial interfaces)

Traffic from site A to Site B and vice versa is via P2P Link.

We use some eigrp distance tweaking on remote site A and B so that eigrp learnt routes are preferred over EBGP routes.

What is required?

Let's say router A's MPLS is tear down,  the traffic path

1) From site A to B, is already via P2P (the primary link)

2) From Site A to any remote sites should also route via P2P. This is the requirement.

Similarly, when Router B's MPLS is dow, the other way round should also work.

Few Questions :

*************

1.           Is it good to peer Router A and Router B via iBGP? 

                      - I will use network command to advertise all prefixes at both ends- ruouter A and router B.

Now, rouer  A and Router B will both hase an IGP matching route in the routing table and then advertised via network command. will both advertise into the cloud ?

                      - May be I can use path atribute like a prepend to influence the router

                      - Earlier we has issues when advertising the same prefix from two location (thread 3728134) Should I use community attribute to distinguish the routes?

                      - What are other things I should take into consideration?

                      - Do you see any design docs for this?

2.          Use simple EIGRP to BGP with mutual redistribution at two points -A and B ?

3.            Use policy based routing setting next hop for both Router A and B's traffic at LAN interface and then use to static to bgp redistribution with route tracking of remote sites?

[Praveen AR]

Hi vinayaka,

1. Is it good to peer Router A and Router B via iBGP?

- I will use network command to advertise all prefixes at both ends- ruouter A and router B.

Now, rouer A and Router B will both hase an IGP matching route in the routing table and then advertised via network command. will both advertise into the cloud ?

- May be I can use path atribute like a prepend to influence the router

- Earlier we has issues when advertising the same prefix from two location (thread 3728134) Should I use community attribute to distinguish the routes?

- What are other things I should take into consideration?

- Do you see any design docs for this?

Yes you can run IBGP between both routers and you can influence outgoing path through  Router A setting  high weight on Router A..

Also if you want  to influence incoming path you can send AS-path attribute or MED.

2. Use simple EIGRP to BGP with mutual redistribution at two points -A and B ?

Yes this is another solution ,you can do mutual redsitribution.

Here you have to change AD for routes you want to directly from router A to Router B(without crossing provider)

3. Use policy based routing setting next hop for both Router A and B's traffic at LAN interface and then use to static to bgp redistribution with route tracking of remote sites

Polcy based routing  is little complicated.

Regards

Praveen