MPLS label got 4 bytes and is inserted between L2 and L3. It encapsulates the L2 frame. the first 20 bits is label itself, which is assigned to each packet. next 3 bites is EXP filed which contain QoS or IPPresence values. next one bit is bottom of stack indicator. This indicates if the label  Full Article…

Pre-requirements CEF must be enabled – without CEF the MPLS just doesnt work IGP routing – for router to be able to map label to network the route must exist in routing table for that network. Router build from routing table the FIB in CEF and once you configure label binding it will configure also  Full Article…

First the router build routing table for IGP routing in MPLS domain and put it to FIB in CEF Every LSR assign a local label for each route learned Every LSR assign implicit null label for its local connected interface networks. Every LSR will share its label with its direct neighbors using LDP Every LSR  Full Article…

Penultimate Hop Popping optimizes MPLS performance by removing the requirement for double lookup to be performed on PE router. The LIB table will show the value of imp-null. When PHP is turned on the penultimate router remove the label (POP) from the packet if he sees that the destination packet is directly connected for the  Full Article…

When your MPLS neighbors are not forming the neighborship, you may have these possible issues: MPLS IP not enabled on interface protocol missmatch (TDP, LDP globaly or at interface level) higher loopback ID is taken as a router ID which is not advertised via IGP missmatch authentication if configured filtering udp port 646 for LDP  Full Article…

Here are basic steps how to configure MPLS L3 VPN: Configure IGP inside SP Core Configure MPLS LDP inside SP Core Create VRF, RD and RT for customer Configure VPNv4 peering between PE routers Configure routing between PE and CE – you provide whatever customer requires here (OSPF, static, BGP, ISIS, RIP,…) Configure redistribution on  Full Article…

VRF means Virtual Routing Forwarding and it allows you to create more than one routing tables inside one physical routers, hence creating many virtual routers. You can then assign specific interfaces to related VRFs. The Route-Distinguisher (RD) & Route-Target (RT) are two different concepts that are both used in an MPLS VPN. The RD is  Full Article…