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

Convergence and High Availability · Lesson 01 of 01

Failing over faster than the timers

Default BGP convergence is measured in minutes. BFD, next-hop tracking and PIC bring it down to sub-second when the design needs it.

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

Written lesson

Why default is slow

The default hold timer is 180 seconds — BGP will wait that long before declaring a silent neighbour dead. Even with tuned keepalives, detecting a failure through BGP alone is slow. The faster path is to detect the failure elsewhere and tell BGP immediately: link-down events, IGP next-hop withdrawal, or a dedicated liveness protocol. BGP timers are the last resort, not the first line of defence.

Written lesson

BFD, next-hop tracking, PIC

BFD (Bidirectional Forwarding Detection) is a lightweight hello protocol that detects a path failure in milliseconds and signals BGP to tear the session down at once, bypassing the hold timer. BGP next-hop tracking watches the RIB and reacts the instant the IGP withdraws the route to a next hop, rather than waiting. PIC (Prefix Independent Convergence) pre-installs a backup path in the FIB so failover does not depend on reconverging every prefix one by one — the whole table switches to the backup in one operation.

Configuration

BFD for a BGP neighbour

IOS / IOS XE
interface GigabitEthernet0/0
 bfd interval 300 min_rx 300 multiplier 3
!
router bgp 65001
 neighbor 10.12.0.2 fall-over bfd

Graceful Restart is the opposite goal

GR and NSR keep forwarding alive while the control plane restarts — they hide a restart rather than speed a failover. Use fast-failover tools for real failures and GR/NSR for planned or software-level control-plane events.