Linux – Multihomed BGP linux router

Here's another example, with basic filtering (no RFC1918 inbound routes, only advertise your local prefix:

router bgp YOURASN
 bgp router-id BGP_ROUTER_IP_ADDRESS
 network 209.85.171.0/24
 neighbor myisp peer-group
 neighbor myisp remote-as ISPASN
 neighbor myisp distribute-list 3 in
 neighbor myisp distribute-list 4 out
 neighbor myisp filter-list 2 out
 neighbor ISP_ROUTER_IP_ADDRESS peer-group myisp
 distance bgp 150 150 150
!
access-list 3 deny 10.0.0.0 0.0.0.255
access-list 3 deny 192.168.0.0 0.0.255.255
access-list 3 deny 172.16.0.0 0.15.255.255
access-list 3 permit any
access-list 4 permit 209.85.171.0 0.0.0.255
!
ip as-path access-list 2 permit ^$

I think that what you need here is a link between your two datacentres. I'm thinking dark fiber would be your best option as you can do pretty anything you want with it but any other L2 link will do the trick.

Considering such a link, you will be able to have all your edge routers in the same VRRP/HSRP/CARP group. You will need to configure them in the same way. I think you should do this for every network equipement that has a reason to be in each datacenter.

Using such redundancy, the primary router will announce your routes to the world and the secondary router will just wait for it to fail. If your datacenter fails, the secondary will take over. If your primary router fails, it will also take over which could be a problem. This is why you want to have bidirectionnal communication between your datacenters.

This link will also be extremely helpful for other tasks such as SAN replication which you will most likely want.