High Availability; Preferred Tunnel Path; Multisegment Pseudowire - Cisco ASR 9000 Series Configuration Manuallines

High Availability

High Availability
L2VPN uses control planes in both route processors and line cards, as well as forwarding plane elements in
the line cards.
The availability of L2VPN meets these requirements:
• A control plane failure in either the route processor or the line card will not affect the circuit forwarding
• The router processor control plane supports failover without affecting the line card control and forwarding
• L2VPN integrates with existing Label Distribution Protocol (LDP) graceful restart mechanism.

Preferred Tunnel Path

Preferred tunnel path functionality lets you map pseudowires to specific traffic-engineering tunnels. Attachment
circuits are cross-connected to specific MPLS traffic engineering tunnel interfaces instead of remote PE router
IP addresses (reachable using IGP or LDP). Using preferred tunnel path, it is always assumed that the traffic
engineering tunnel that transports the L2 traffic runs between the two PE routers (that is, its head starts at the
imposition PE router and its tail terminates on the disposition PE router).
Note
• Currently, preferred tunnel path configuration applies only to MPLS encapsulation.

Multisegment Pseudowire

Pseudowires transport Layer 2 protocol data units (PDUs) across a public switched network (PSN). A
multisegment pseudowire is a static or dynamically configured set of two or more contiguous pseudowire
segments. These segments act as a single pseudowire, allowing you to:
• Manage the end-to-end service by separating administrative or provisioning domains.
• Keep IP addresses of provider edge (PE) nodes private across interautonomous system (inter-AS)
A multisegment pseudowire can span either an inter-AS boundary or two multiprotocol label switching (MPLS)
networks.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
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path.
planes.
boundaries. Use IP address of autonomous system boundary routers (ASBRs) and treat them as pseudowire
aggregation routers. The ASBRs join the pseudowires of the two domains.
Implementing Point to Point Layer 2 Services