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

Multipath and Load Sharing · Lesson 01 of 01

Installing more than one path

By default BGP installs one best path. Multipath lets equal-cost paths share the load — if they are truly equal where it counts.

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

Written lesson

What must match

For BGP multipath, candidate paths must tie on everything best-path compares up to the IGP metric: same weight, local-pref, AS_PATH length, origin, MED, and the same type (all eBGP or all iBGP). Crucially, by default the AS_PATH must be identical, not merely the same length — bgp bestpath as-path multipath-relax loosens that to same-length paths through different AS's, which is what you usually want with two providers.

Configuration

eBGP multipath with relax

IOS / IOS XE
router bgp 65001
 address-family ipv4 unicast
  maximum-paths 2
  bgp bestpath as-path multipath-relax

Best is still best

Even with multipath, BGP advertises only the single best path to neighbours. Multipath changes forwarding (the RIB/FIB), not what you announce. Diversity for downstream routers still needs Add-Path or design.