VPLS Overview Configuring VPLS
page 11-8 OmniSwitch AOS Release 6 Network Configuration Guide September 2009
Example MPLS-Based VPLS Network
VPLS MAC Learning and Packet Forwarding
The OmniSwitch performs the packet replication required for broadcast and multicast traffic across the
bridged domain. MAC address learning is performed by the OmniSwitch to reduce the amount of
unknown destination MAC address flooding.
Each OmniSwitch maintains a Forwarding Information Base (FIB) for each VPLS service instance. Source
MAC addresses arriving on OmniSwitch access and network ports are learned.and populated in the FIB
table of the service.
All traffic is switched based on MAC addresses and forwarded between all participating routers using the
LSP tunnels. Unknown destination packets are forwarded on all LSPs to the participating routers for that
service until the target station responds and the MAC address is learned by the router associated with that
service.
Loop Prevention
To prevent forwarding loops, the "Split Horizon" rule is used. In the VPLS context, this rule implies that a
PE must never send a packet on a pseudowire (PW) if that packet was received from a PW. This ensures
that traffic cannot form a loop over the backbone network using PWs.
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