Related
Documentation
Pseudowire Overview for ACX Series Universal Access Routers on page 590•
• TDM Pseudowires Overview on page 600
Redundant Pseudowires for Layer 2 Circuits and VPLS
A redundant pseudowire can act as a backup connection between PE routers and CE
devices, maintaining Layer 2 circuit and VPLS services after certain types of failures. This
feature can help improve the reliability of certain types of networks (metro for example)
where a single point of failure could interrupt service for multiple customers. Redundant
pseudowires cannot reduce traffic loss to zero. However, they provide a way to gracefully
recover from pseudowire failures in such a way that service can be restarted within a
known time limit.
NOTE: VPLS is not supported on ACX Series routers.
When you configure redundant pseudowires to remote PE routers, you configure one to
act as the primary pseudowire over which customer traffic is being transmitted and you
configure another pseudowire to act as a backup in the event the primary fails. You
configure the two pseudowires statically. A separate label is allocated for the primary
and backup neighbors.
For information about how to configure redundant pseudowires, see “Configuring
Redundant Pseudowires for Layer 2 Circuits and VPLS” on page 606.
The following sections provide an overview of redundant pseudowires for Layer 2 circuits
and VPLS:
•
Types of Redundant Pseudowire Configurations on page 604
•
Pseudowire Failure Detection on page 605
Types of Redundant Pseudowire Configurations
You can configure redundant pseudowires for Layer 2 circuits and VPLS in either of the
following manners:
NOTE: VPLS is not supported on ACX Series routers.
•
You can configure a single active pseudowire. The PE router configured as the primary
neighbor is given preference and this connection is the one used for customer traffic.
For the LDP signalling, labels are exchanged for both incoming and outgoing traffic
with the primary neighbor. The LDP label advertisement is accepted from the backup
neighbor, but no label advertisement is forwarded to it, leaving the pseudowire in an
incomplete state. The pseudowire to the backup neighbor is completed only when the
primary neighbor fails. The decision to switch between the two pseudowires is made
by the device configured with the redundant pseudowires. The primary remote PE
Copyright © 2017, Juniper Networks, Inc.604
ACX Series Universal Access Router Configuration Guide
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