Bgp-Based Vpls Autodiscovery; Bgp Auto Discovery With Bgp Signaling - Cisco CRS Configuration Manual

Implementing Multipoint Layer 2 Services

BGP-based VPLS Autodiscovery

An important aspect of VPN technologies, including VPLS, is the ability of network devices to automatically
signal to other devices about an association with a particular VPN. Autodiscovery requires this information
to be distributed to all members of a VPN. VPLS is a multipoint mechanism for which BGP is well suited.
BGP-based VPLS autodiscovery eliminates the need to manually provision VPLS neighbors. VPLS
autodiscovery enables each VPLS PE router to discover the other provider edge (PE) routers that are part of
the same VPLS domain. VPLS Autodiscovery also tracks when PE routers are added to or removed from the
VPLS domain. When the discovery process is complete, each PE router has the information required to setup
VPLS pseudowires (PWs).
Even when BGP autodiscovery is enabled, pseudowires can be manually configured for VPLS PE routers
that are not participating in the autodiscovery process.

BGP Auto Discovery With BGP Signaling

The implementation of VPLS in a network requires the establishment of a full mesh of PWs between the
provider edge (PE) routers. The PWs can be signaled using BGP signaling.
Figure 15: Discovery and Signaling Attributes
The BGP signaling and autodiscovery scheme has the following components:
• A means for a PE to learn which remote PEs are members of a given VPLS. This process is known as
autodiscovery.
• A means for a PE to learn the pseudowire label expected by a given remote PE for a given VPLS. This
process is known as signaling.
The BGP Network Layer Reachability Information (NLRI) takes care of the above two components
simultaneously. The NLRI generated by a given PE contains the necessary information required by any other
PE. These components enable the automatic setting up of a full mesh of pseudowires for each VPLS without
having to manually configure those pseudowires on each PE.
Cisco IOS XR Virtual Private Network Configuration Guide for the Cisco CRS Router, Release 6.1.x
VPLS Discovery and Signaling
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