Preventing persistent oscillations and loops in IBGP configuration with route reflection

Abstract-- Internal Border Gateway Protocol (IBGP) is responsible for distributing external reachability information, obtained via External-BGP (EBGP) sessions, within an autonomous system (AS). To avoid a full mesh of IBGP sessions between all the BGP speakers of an AS, scaling schemes such as route reflection and AS confederations have been proposed. But it has been observed that employing these schemes may result in problems such as routing oscillations and forwarding loops due to MultiExit Discriminator (MED) attribute and path asymmetry in IBGP. In this paper we study the pathologies observed in IBGP when route reflection is used. We model the AS using the Interior Gateway Protocol (IGP) connectivity graph GI and IBGP peering graph GL. Then we state some simple conditions on GI and GL and prove that these conditions guarantee the absence of any persistent routing oscillations and forwarding loops due to MED attribute and IBGP path asymmetry. We consider the problem of constructing...

• Type: Journal
• Year: 2006
• Where: CN
• Authors: Anuj Rawat, Mark A. Shayman
• Keywords: CN 2006, IBGP, Persistent Routing Oscillation, Route Reflection