Pseudowire Redundancy
Pseudowire redundancy allows you to configure your network to detect a failure in the network and reroute
the Layer 2 service to another endpoint that can continue to provide service. This feature provides the ability
to recover from a failure of either the remote provider edge (PE) router or the link between the PE and customer
edge (CE) routers.
L2VPNs can provide pseudowire resiliency 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 takes over.
However, there are some parts of the network in which this rerouting mechanism does not protect against
interruptions in service.
Pseudowire redundancy enables you to set up backup pseudowires. You can configure the network with
redundant pseudowires and redundant network elements.
Prior to the failure of the primary pseudowire, the ability to switch traffic to the backup pseudowire is used
to handle a planned pseudowire outage, such as router maintenance.
Pseudowire redundancy is provided only for point-to-point Virtual Private Wire Service (VPWS) pseudowires.
Note
Pseudowire Load Balancing
To maximize networks while maintaining redundancy typically requires traffic load balancing over multiple
links. To achieve better and more uniformed distribution, load balancing on the traffic flows that are part of
the provisioned pipes is desirable. Load balancing can be flow based according to the IP addresses, Mac
addresses, or a combination of those. Load balancing can be flow based according to source or destination IP
addresses, or source or destination MAC addresses. Traffic falls back to default flow based MAC addresses
if the IP header cannot proceed or IPv6 is be flow based.
This feature applies to pseudowires under L2VPN; this includes VPWS and VPLS.
Enabling virtual circuit (VC) label based load balancing for a pseudowire class overrides global flow based
load balancing under L2VPN.
Note
Pseudowire Grouping
When pseudowires (PWs) are established, each PW is assigned a group ID that is common for all PWs created
on the same physical port. When a physical port becomes non-functional or disabled, Automatic Protection
Switching (APS) signals the peer router to get activated and L2VPN sends a single message to advertise the
status change of all PWs that have the Group ID associated with the physical port. A single L2VPN signal
thus avoids a lot of processing and loss in reactivity.
For CEM interfaces, various levels of configuration are permitted for the parent controllers, such as T1 and
T3, framed or unframed. To achieve best grouping, the physical controller handle is used as the group ID.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
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Implementing Point to Point Layer 2 Services
Pseudowire Redundancy
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