Administrator Guide

BGP 1325
Figure 39-1. BGP Decision Process
BGP Route Selection
Dell Networking BGP uses the following route selection rules in order from 1
to N:
1
Prefer the route with the higher local preference
2 Prefer a locally-originated route over a non-locally originated route
3 Prefer the route with the shorter AS Path
4 Prefer the route with the lower ORIGIN. IGP is better than EGP is better
than INCOMPLETE.
5 Prefer the route with the lower MED. By default, MEDs are compared for
routes from any AS, but a configuration option limits comparison of
MEDs to the same AS. A route with no MED is considered to have a MED
of 0.
6 Prefer an eBGP route to an iBGP route
7 Prefer the route with the lower IGP cost to the BGP NEXT HOP
8 Prefer the route learned from the peer with the lower router ID
9 Prefer the route learned from the peer with the lower peer IP address
Update
Update
RX
Adj-
RIB-In
DEC PROC P1
(inbound policy,
calc local pref)
Accept-
RIB-In
Loc-RIB
Adj-RIB
Out
Adj-RIB-
Out
Adj-RIB-
Out
Update
DEC PROC P3
(outbound policy,
incl. aggregation)
RTO
Pass redist
Policy?
Network
routes
DEC
PROC P2
(best route
selection)
Best route
changes
yes
Next-hop
resolution