Vpls Multihoming Reactions To Network Failures - Juniper EX9200 Features Manual

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VPLS Multihoming Reactions to Network Failures

Copyright © 2016, Juniper Networks, Inc.
route reflector, the path selection process for the multihomed site has no effect on the
path selection process performed by this PE router for the purpose of reflecting Layer 2
routes. Layer 2 prefixes that have different route distinguishers are considered to have
different NLRIs for route reflection. The VPLS path selection process enables the route
reflector to reflect all routes that have different route distinguishers to the route reflector
clients, even though only one of these routes is used to create the VPLS pseudowire to
the multihomed site.
Junos OS supports VPLS multihoming for both FEC 128 and FEC 129. Support for FEC
129 is added in Junos OS Release 12.3.
Configuring VPLS Multihoming (FEC 128) on page 66
Advantages of Using Autodiscovery for VPLS Multihoming
Example: Configuring VPLS Multihoming (FEC 129)
Example: VPLS Multihoming, Improved Convergence Time
VPLS multihoming is designed to protect customer sites from a loss of network
connectivity in the event of the following types of network failures:
Link failure between the CE device and the PE router—BGP on the PE router is notified
when the link goes down. BGP sets the circuit status vector bit in the MP_REACH_NLRI
to indicate that the circuit is down.
If all of the VPLS local attachment circuits are down, then BGP modifies the down bit
in the VPLS advertisement Layer2-Extended-Community to indicate that the customer
site is down. When the bit is modified, BGP advertises the route to all of the remote
PE routers to notify them that the circuit (and site) is down. Each of the remote PE
routers run the BGP and VPLS path selection procedures again and reroute the VPLS
pseudowires as needed.
MPLS connectivity failure to the remote PE router—On the multihomed PE router, BGP
discovers that MPLS cannot connect to the BGP next hop in the service provider's
network. BGP modifies the circuit status vector bit in the MP_REACH_NLRI to indicate
that the LSP is down. Once the bit is modified, BGP readvertises the route to all of the
remote PE routers to notify them that connectivity from the local site to the remote
site is down.
The remote PE routers each run the BGP and VPLS path selection procedures again.
With the LSP to the original multihomed PE router down, the remote PE routers
designate the backup multihomed PE router as the VE device for the multihomed
customer site. The pseudowires to and from the remote PE routers are then rerouted
to the backup multihomed PE router.
PE router failure—When either the multihomed PE router or the BGP process running
on it fails, the remote PE routers detect the expiration of the holdtimer, bring down
their peering sessions, and delete the Layer 2 advertisements from that multihomed
PE router. The remote PE routers each run the BGP and VPLS path selection procedures
again and reroute their pseudowires to the backup multihomed PE router.
Chapter 7: Configuring Multihoming
63