- BGP routing becomes more complex in networks that span multiple locations, requiring consideration of using iBGP with loopback addresses, propagating loopback and next hop addresses, using route reflectors instead of a full iBGP mesh, where to originate prefixes, and filtering announcements.
- When using iBGP between locations, loopback addresses should be used instead of interface addresses to avoid sessions going down if links fail, and the loopback addresses must be propagated via an IGP. Next hop addresses for eBGP routes must also be propagated or replaced.
- Route reflectors can be used instead of a full iBGP mesh to avoid having sessions between all routers, with clients, non-clients, and a possible hierarchy of route