Limitations; Pseudowire Redundancy - Cisco CRS Configuration Manual

Implementing Point to Point Layer 2 services
• The forwarding occurs based on the Layer 2 VC label on the packet.
• A VC label lookup identifies the correct Layer 2 circuit to be used, to forward the packet towards the

Limitations

• Fragmentation and reassembly of GRE packets are not supported.
• At GRE tunnel head end, decision to fragment packet is taken on the basis of Do-Not-Fragment (DF)
• The configured tunnel GRE DF flag value is inserted into transport header. However, fragmentation of
• The following features are not supported:

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)
Note
pseudowires.
CE router that hosts the Layer 2 destination.
flag in IPv4 header of the incoming packet. The GRE tunnel DF flag configuration is ignored while
fragmenting the packet.
GRE packet is not supported anywhere in the GRE tunnel path.
◦ GRE tunnel in VRF domains
◦ Multicast
◦ V6 over GRE
◦ MPLS/L3VPN over GRE
◦ VPNv4 forwarding over GRE tunnels
◦ 6PE/6VPE over GRE
Cisco IOS XR Virtual Private Network Configuration Guide for the Cisco CRS Router, Release 6.1.x
Pseudowire Redundancy
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