CCIE Enterprise Infrastructure · BGP

BGP — CCIE Enterprise Infrastructure

The complete BGP learning path for CCIE Enterprise Infrastructure: how sessions form, how prefixes are chosen and shaped, how the protocol scales with route reflection and confederations, and how it is designed, secured and repaired in production.

  • 24 complete lessons
  • 5 hr 20 min
  • Foundation

The BGP Table · Lesson 01 of 01

Reading the BGP table

The BGP table is not the routing table. Learning to read its codes is half of BGP troubleshooting.

  • 12 min lesson
  • 00:00 video
  • Foundation
Written lessonConfiguration

Written lesson

Three tables, one output

Conceptually BGP keeps three: the Adj-RIB-In (everything a neighbour sent, before your inbound policy), the Loc-RIB (what survived policy and best-path — what show bgp displays), and the Adj-RIB-Out (what you send each neighbour after outbound policy). IOS does not store the full Adj-RIB-In unless you enable soft-reconfiguration inbound; that is why a route you expected to see may simply have been filtered before it was stored.

show bgp ipv4 unicast
show bgp ipv4 unicast 192.0.2.0/24
show bgp ipv4 unicast neighbors 10.12.0.2 received-routes

Written lesson

The codes that matter

In show bgp, the leading characters carry the meaning. * means the path is valid; > marks the one chosen as best and installed into the RIB. i in the first column means the route was learned by iBGP. A path with no > was valid but lost best-path. r means RIB-failure (BGP chose it but the RIB rejected it, often because a better-AD route already owns the prefix). s means suppressed by aggregation. Reading these before anything else tells you whether the problem is selection, installation or filtering.

received-routes needs soft-reconfig

received-routes shows the Adj-RIB-In and only works if neighbor x soft-reconfiguration inbound is configured or route-refresh is negotiated. routes (what you accepted) always works.