This post contains my notes from an old version of IPX Class on Demand by Joe Astorino.
# hiding MPLS topology by just incrementing TTL 1 time when reaching the CErouter(config)# no ip mpls propagate-ttl
MPLS MTU is automatically decreased on LAN interfaces and increased on WAN interfaces.
Default mpls mtu is 1512 which supports 3 labels; MPLS MTU can be set by mpls mtux
LDP router-id should be routable on network.
router(config)# mpls ldp advertise-labels [for acl] [to peer]router(config)# mpls ldp range x y!# Enabling MPLS on all OSPF interfaces or an arearouter(config-router)# mpls ldp autoconfig [area x]!router(config)# mpls ldp discovery holdtime xrouter(config)# mpls ldp graceful-restart // NSF within LDProuter(config)# mpls ldp loop-detectionrouter(config)# mpls ldp max hops xrouter(config)# tag-switching tdp router-id loopback0 // If TDP is used.# Using separate update-source for an interfacerouter(config-if)# mpls ldp discovery transport-address interface
Connected routes are advertised as implicit-null label for PHP on upstream router
router(config)# mpls ldp neighbor ip labels accept aclrouter(config)# mpls ldp tcp pak-priority //Kinda like setting QoS for LDP!#Like "ip accounting"router(config-if)# mpls accounting experimental input/outputrouter(config-if)# mpls netflow egress!router# show mpls ldp binding // LIBrouter# show mpls forwarding table // LFIBrouter# show ip route // RIBrouter# show ip cef ip detail //FIB
IP routers make forwarding decision based on IP packet header, and local CEF and FIB table.
MPLS routers make forwarding decision based on the MPLS label and the LFIB .
MPLS is great technology these days not because it forwards the packets faster , but because of applications and solutions we can provide for our customers like MPLS VPN’s .
MPLS uses the IP routing information to determine the direction and next hop to forward a labeled packet .
Most popular were Frame Relay or ATM technologies, providing VPN service at Layer 2. The provider had a Frame Relay or ATM backbone and supplied Layer 2 connectivity to the customer routers. This was commonly referred to as the overlay model.
The service provider might have actually owned or managed the edge routers that were connected to the customer network. The point is that the routers were physically at the customer premises.
Peer-to-peer VPN networks existed, but they were not popular. The main reason is that they were not easy to deploy and maintain because they needed distribute lists, IP packet filters, or GRE tunnels. As explained in Chapter 1, MPLS VPN is an example of a highly scalable peer-to-peer VPN model.
The CE router does not peer with any of the CE routers from the other sites across the service provider network, as with the overlay model. The name peer-to-peer model is derived from the fact that the CE and PE form a peer at Layer 3.
Virtual routing/forwarding (VRF): is a VPN routing and forwarding instance. It is the name for the combination of the VPN routing table, the VRF Cisco Express Forwarding (CEF) table, and the associated IP routing protocols on the PE router.