Introduction to L2VPN Pseudowire Redundancy in MPLS Networks

Today I am going to talk about L2VPN Pseudowire Redundancy. This feature is used in the case of the L2 network connectivity across your sites via service providers. The L2VPN Pseudowire Redundancy feature permits to configure the network and to identify a catastrophe in the network and redirect the Layer 2 (L2) service to another endpoint that can endure to deliver service. 

This feature delivers the capability to retrieve from a catastrophe either of the remote provider edge (PE) router or of the link between the PE and customer edge (CE) routers.

L2VPNs can deliver Pseudowire resiliency via their routing protocols. When connectivity among end-to-end PE routers stops, another path to the guided LDP session and the user data can take over. Though, there are some parts of the network where this redirecting mechanism does not defend beside disruptions in service. 

Fig 1.1- Pseudowire L2VPN Connectivity

Restrictions for L2VPN Pseudowire Redundancy
  • The LDP session hold-down timer will allow the software to notice catastrophes within 180 seconds. That time can be configured so that the software can detect failures more quickly. 
  • Make a note of it that the L2VPN Pseudowire Redundancy does not support Pseudowire interworking mode with L2TPv3.
  • Take this in consideration that the primary and backup pseudowires always run the same type of transport service. The primary and backup pseudowires always be configured with AToM or L2TPv3.
  • L2VPN Pseudowire Redundancy does support setting the experimental (EXP) bit on the Multiprotocol Label Switching (MPLS) Pseudowire and the mpls l2transport route command is not supported. Use the xconnect command instead

Configuring the Pseudowire
RouteXP_Router> enable
RouteXP_Router # configure terminal
RouteXP_Router (config)# pseudowire-class atom
RouteXP_Router (config-pw-class) # encapsulation mpls
RouteXP_Router (config-pw-class) # interworking ip

Configuring the Pseudowire using the commands associated with the L2VPN Protocol-Based CLIs feature
RouteXP_Router > enable
RouteXP_Router # configure terminal
RouteXP_Router (config)# interface pseudowire 1
RouteXP_Router (config-pw-class) # encapsulation mpls
RouteXP_Router (config-pw) # neighbor 123
RouteXP_Router (config-pw) # interworking ip

Configuring L2VPN Pseudowire Redundancy
RouteXP_Router > enable
RouteXP_Router # configure terminal
RouteXP_Router (config)# interface gigabitethernet0/0/0.1
RouteXP_Router (config-subif) # encapsulation dot1q 100
RouteXP_Router (config-subif) # xconnect 123 pw-class atom
RouteXP_Router (config-if-xconn) # backup peer 125 pw-class atom
RouteXP_Router (config-if-xconn) # backup delay 10 never

Verifying the L2VPN Pseudowire Redundancy Configuration
RouteXP_Router # show mpls l2transport vc
RouteXP_Router # show mpls l2transport vc detail
RouteXP_Router # show xconnect all
RouteXP_Router (config)# xconnect logging redundancy
RouteXP_Router # show l2vpn atom vc detail
RouteXP_Router # show l2vpn service all