removing a BGP router

When you wnat to remove a device that is running IBGP, you have to watch where IBGP sessions can form. I was removing a router with had IBGP configured on it to another router at a site that was connected to MPLS providers. The LAN interfaces were shut down. What happened next was since the router loopbacks (the IBGP neighbors) were put into the provider and IBGP session would form through the providers with a long as path. Now you would think that BGP split horizon would prevent router A from learning about router B, BUT if you have a default route, traffic will flow to your data center that will know about both loopbacks via the providers and will route traffic between them Then prefixes for the local subnets began to flow to the router that had no connection to the local networks. Then that router advertised them to the provider so traffic started to flow to a router that could not forward any of that traffic. Finally router A would send via IBGP its own loopback that would point to a local route, since router B was not connected to the any LANs once that IBGP advertisement of the loopback arrived, the IBGP session would time out, then the local based loopback prefix gets removed the prefix advertised by the provider comes back. THUS the ibgp peer goes up and down in a 90 second sequence. Net of this is that if you are removing a device from the network, first thing to do is to shut down dynamic routing to that box, add any static routes to say loopbacks you need and a default route to the device being removed, then after a while shut down the interfaces.