BGP with three ISPs

[netsec123]

Hi. We are connected to three different ISPs. Two in location A and one in location B. Location A and B are connected via dedicated circuit. So there are three routers and three ISPs. Is there an example out there somewhere that allows me to use all three and failover to the alternate site if the Internet goes down locally?

Thanks!

[netsec123]

Dandy, I think that's an excellent idea. The only issue is that we brought that up and priced the DS3 cards - BIG BUCKS! That's why we did not go with it... :( BUT, it is very reassuring to see we are thinking along the same path.

TF :)

[Danilo Dy]

Hi,

Any chance to replace DS3 with MetroE or MPLS?

MetroE and MPLS use Ethernet which you may have a spare port in your routers, have you check the migration cost (one-time and recurring)?

Regards,

Dandy

[netsec123]

You're making me cry... :)

I can't replace any hardware here --- unfortunately, it is what it is... I know that makes things more difficult - sorry...

[Rick Morris]

Sort of. For failover and redundancy you need all your routes to be announced to all your providers. However, they may not allow you to route other vendor IP's.

You will also need to have some routing protocol between your sites so you can route through them. I think I saw medan's post about GRE. This is one option, or iBGP between your sites.

[netsec123]

I would like to use iBGP and I 'thought' I had that configured already... including on the router that did NOT terminate an Internet line from an ISP but DID connect the sites... Does that make sense?

[Danilo Dy]

Hi,

See if you can do this...let me know the constraint if you can't.

- Both R4, R2, and R1 should have direct physical connection to R3. R4 (DS3), R2 and R1 (direct ethernet or through switch)

- Configure IP GRE between R2 and R4 through R3

- Configure IP GRE between R1 and R4 through R3

- Create Loopback interfaces in R4, R2, and R1 to be use for BGP

- Run BGP/iBGP in R4, R2, and R1 using ASN11821

- Advice QWEST, LP, and VZ to allow your prefixes (all prefixes) as they have ACL what to permit from you.

- Peer with QWEST, LP, and VZ using ASN11821 advertising your prefixes

Regards,

Dandy

[netsec123]

Hi, THANKS. I will try this... I was unaware I needed to do GRE tunnels if BGP routers were not directly connected. I thought if they were in the same iBGP AS routes would propagate [i.e. ALL R1 --> R4 running ASN11821] .. Am I wrong?

[Rick Morris]

I am not sure why the GRE if running iBGP.

If you are announceing your blocks between your routers then you will propigate the routing table. That should be all you need. I am not sure why the GRE is mentioned in the previous post.

[netsec123]

Yes -- That's why I mentioned in my last post the same thing -- GRE may should [should not?] be needed....

TF