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.
ORF pushes your inbound prefix filter to your BGP neighbor so unwanted routes never leave their router. Shown working on Cisco IOS XE with real CML output, including the commands the receiving router uses to see the filter you sent it.
BGP conditional advertisement withholds a prefix until a condition you define is no longer true. Walk through advertise-map, exist-map, and non-exist-map on Cisco IOS XE to keep a backup path truly idle.
VXLAN without a control plane is flood-and-learn, and that does not scale to a real data center. BGP EVPN is what fabrics actually use: what it advertises, the route types that carry reachability, and why it replaced flooding everywhere.
An L3VPN route can quietly disappear at six points between customer VRF and remote CE, none of them logging an error. This article gives you a repeatable path to walk the route, with captures from a live five-router IOS XE lab with induced failures.
Route distinguishers make prefixes unique; route targets control which VRFs import them. They look identical and do unrelated jobs, and this article proves it with one BGP table holding the same prefix twice.
Static, OSPF, EIGRP, or eBGP: the PE-CE protocol decides what the customer sees and how fast the L3VPN reconverges. This article runs three of them back to back on the same MPLS lab and shows exactly what changes.
Configure MPLS L3VPN step by step: VRF, RD, RT, LDP, and MP-iBGP carrying VPNv4 between PE routers. Every command and every line of output comes from a five-router Cisco IOS XE lab running OSPF as the core IGP.
Default hello timers take tens of seconds to notice a dead neighbor. This post configures BFD on Cisco IOS XE and races it against OSPF defaults: 34 seconds without BFD, 0.58 seconds with it, captured live with a stopwatch.
Basic BGP peering takes half a dozen lines; what trips people up is eBGP vs iBGP behavior, getting routes into BGP, and the iBGP next-hop quirk that silently breaks reachability. A full IOS XE walkthrough.
BGP weight is the first tiebreaker in the path-selection algorithm, set locally and never propagated. The three ways to set it, how it compares to LOCAL_PREF, and worked examples.
BGP looking glasses explained: what they show, the public servers worth bookmarking, a four-step troubleshooting recipe, and how to host your own with hyperglass.
When OSPF and BGP both know about the same prefix, who wins? A practical walkthrough of mutual redistribution, the admin-distance trap, and why BGP into OSPF needs a filter or it takes down your domain.