Troubleshooting Tips
BGP routing loop?
First, check for IGP routing loops to the BGP NEXT_HOPs
BGP loops are normally caused by
Not following physical topology in RR environment
Multipath with confederations
Lack of a full iBGP mesh
Get the following from each router in the loop path
show ip route x.x.x.x
show ip bgp x.x.x.x
show ip route NEXT_HOP