Hierarchical Vpls (H-Vpls) - Extreme Networks Ridgeline Guide Manual

Managing and Monitoring VPLS Domains

Hierarchical VPLS (H-VPLS)

When MPLS is used at the edge of the network, a fully meshed VPLS domain becomes less practical,
due to the number of PWs that must be configured between a large number of peers. A hierarchical
VPLS (H-VPLS) network can improve network scalability by reducing the number of PWs that need to
be configured between peers.
In an H-VPLS domain, VPLS domains can be constructed hierarchically in a partial-mesh or hub-and-
spoke configuration. Within the context of H-VPLS, a spoke is a VPLS connection between two VPLS
peers. Typically, one spoke node provides connectivity to the customer VLAN or customer service
while its peer, a core node, provides repeater connectivity to other VPLS peers.
H-VPLS introduces the concept of core and spoke PW types. In an interconnected fully meshed VPLS
domain, all of the PWs are of the type core. In an H-VPLS domain, PWs at the fully meshed core of the
network are of the type core, and PWs that connect peers at the edge of the network are of the type
spoke.
The forwarding rules for spoke and core pseudo wires are different. Flood traffic received on a core
pseudo wire from another full-mesh core PE must not be transmitted over other core pseudo wires to
other PEs. However, flood traffic received on a core pseudo wire is transmitted on all spoke pseudo
wires in the VPLS domain. Unlike core pseudo wires in a fully meshed VPLS, flood traffic received on a
spoke pseudo wire must be transmitted on all other pseudo wires in the VPLS, including pseudo wires
to other core PEs.
Figure 83 shows an example H-VPLS domain.
Figure 83: H-VPLS (Hub-and-Spoke) network
MTU
MTU
Spoke Pseudo Wire
Core Pseudo Wire
In a hierarchical VPLS domain, a spoke node (often a Multi-Tenant Unit, or MTU) is only required to
establish a pseudo wire to a single core PE. A VPLS core node that has multiple spoke pseudo wires but
no configured core pseudo wires is informally referred to as a hub.
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