BGP

Border Gateway Protocol, the path-vector protocol that holds the internet together and increasingly runs inside enterprise data centers. Articles tagged BGP cover fundamentals, neighbor states, path attributes, best-path selection, traffic engineering, and Cisco IOS XE configuration.

36 posts

BGP

BGP Confederations: An Alternative to Route Reflectors

BGP confederations scale iBGP by dividing the AS into sub-ASes that speak confederation eBGP internally, while appearing as a single AS to the outside world. An alternative to route reflectors with tradeoffs you need to know.

Mar 28, 2026 4 min read

BGP

BGP Route Reflectors: Eliminating the Full Mesh

Ten routers need 45 iBGP sessions. Fifty need 1,225. Route reflectors break the iBGP split-horizon rule in a controlled way, and are the standard scaling tool for iBGP in enterprise and service provider networks.

Mar 28, 2026 4 min read

BGP

BGP Next-Hop-Self: When and Why You Need It

One of the most common iBGP problems is routes that show up in the BGP table but never hit the routing table because the next-hop is unreachable. Here is when next-hop-self is the fix, and when it actually makes things worse.

Mar 28, 2026 5 min read

BGP

How to Configure iBGP Neighbors and Full Mesh

iBGP has rules eBGP does not: split-horizon, full-mesh, and next-hop preservation. Ignore any of them and routes vanish silently from your network. A practical guide to configuring iBGP neighbors and full mesh.

Mar 28, 2026 5 min read

BGP

How to Configure eBGP Neighbors on Cisco IOS XE

A single mismatch in neighbor IP, AS number, or filtering keeps a BGP session down without a helpful error. A practical Cisco IOS XE eBGP configuration walkthrough including dual-homed peering and source/TTL considerations.

Mar 28, 2026 6 min read

BGP

How BGP Advertises Routes: NLRI, Withdrawn Routes, and the Adj-RIB

BGP does not auto-advertise connected interfaces like OSPF. Routes must be injected via network, redistribution, or aggregation. Understand NLRI, withdrawn routes, and the Adj-RIB pipeline to control what you advertise.

Mar 28, 2026 4 min read