Cisco Cisco IOS Software Release 12.2(27)SBC

Before configuring NSF/SSO—L2VPN Pseudowire Redundancy, you should understand the following 
concept:

Currently, the L2 VPNs provide pseudowire resiliency only through their routing protocols. When 
connectivity between end-to-end PE routers fails, an alternative path to the directed LDP session and the 
user data can take over. However, there are some parts of the network where this rerouting mechanism 
does not protect interruptions in service. 

 shows those parts of the network that are vulnerable 

to an interruption in service. 

NSF/SSO—L2VPN Pseudowire Redundancy provides the ability to ensure that the CE2 router in 

 can always maintain network connectivity, even if one or all the failures in the figure occur. You 

can configure the network with redundant pseudowires (PWs) and redundant RPs, which are shown in 
the following figures. 

 shows a network with redundant pseudowires and redundant attachment circuits.

PE1

CE1

P1

P2

PE2

CE2

X1

X2

X3

X4

X1 = End-to-end routing failure
X2 = PE hardware or software failure
X3 = Attachment circuit failure from a line break
X4 = CE hardware or software failure

135057

Primary

pseudowire

PE1

CE1

PE2

CE2

Backup

pseudowire

135058

Redundant
attachment

circuits