Multiprotocol Label Switching, the forwarding paradigm that powers most service provider backbones and large enterprise WANs. Articles tagged MPLS cover labels and the label stack, LDP, L3VPN with MP-BGP and VPNv4, traffic engineering, and segment routing.
OSPF and IS-IS send every flow down the shortest path while parallel links sit idle. MPLS-TE is how you steer traffic onto the paths you choose. This post covers the problem, the components, and why segment routing is changing how it is done.
The border node is where an SD-Access fabric meets everything else, and where IP transit, SDA transit, and Layer 2 handoff get confused. Untangle all three and see how VRF-lite, BGP, and LISP carry traffic out of the fabric.
Five MPLS L3VPN and DMVPN ticket scenarios, each isolated layer by layer: IGP, LDP, MP-BGP, NHRP, IPsec, and the routing on top. The faults and diagnostic commands come from real lab builds.
MPLS gives you a private SLA-backed core; DMVPN gives you cheap encrypted connectivity over any internet link. This article compares the two honestly and shows the standard hybrid designs most enterprise WANs end up running.
When two customer sites share an AS number, BGP loop prevention breaks their MPLS L3VPN on purpose. Reproduce the failure in a CML lab and fix it three ways: as-override, allowas-in, and SoO, with real output for each.
6VPE carries IPv6 L3VPN across an IPv4 MPLS core using the same VRFs, RTs, and MP-BGP sessions you already run. This article builds it in CML and shows the two-label stack that makes it work.
6PE carries IPv6 prefixes across an untouched IPv4 MPLS core using MP-BGP and labels. This post builds a working deployment on Cisco IOS XE and shows the labels, the IPv4-mapped next hops, and an end-to-end IPv6 traceroute.
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.
MPLS forwarding runs on labels, not on IP reachability, so a dead LDP session leaves every green light green while the customer blackholes. Captured on CML with IOS XE 17.18.2: the unusable: no label CEF entry, the full LDP LIB, a hop-by-hop walk to find where the binding stops, and No Label...
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.