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The H-VPLS with LSP access activates the backup link when:
•
The tunnel over which the primary PW is established is deleted, causing the PW to go down.
•
BFD detects a main link failure.
•
The LDP session between the peers of the primary PW goes down, and the PW is deleted as a
result.
Hub-spoke VPLS implementation
In hub-spoke networking, one of the VPLS networking modes, there is one hub site and multiple spoke
sites. The spoke sites (the spoke-CEs) are not permitted to communicate with each other directly; data
transmission between them depends on the hub site (the hub-CE). The PE connecting the hub site is called
the “hub-PE”. PEs connecting the spoke sites are called “spoke-PEs”.
Advantages of hub-spoke networking
In hub-spoke networking, all traffic between spoke sites must go through the hub site, facilitating
centralized management of traffic.
Hub-Spoke networking
Figure 33
Hub-spoke networking
shows a typical hub-spoke networking application. As the MAC address learning in a
hub-spoke network is the same as that in a common network, the following describes only the data
forwarding procedure:
1.
Upon receiving a packet from Spoke-CE 1, Spoke-PE 1 inserts an MPLS label into the packet
according to the VSI to which Spoke-CE 1 belongs and then forwards the packet to Hub-PE.
2.
Receiving the packet from the PW, Hub-PE determines by the MPLS label the VSI that the packet is
for and forwards the packet to Hub-CE directly.
3.
Hub-CE has Layer 2 forwarding function. It processes the packet and then forwards the packet
back to Hub-PE.
4.
Receiving the packet from the AC, Hub-PE determines by the VLAN tag the VSI that the packet is
for, inserts an MPLS label to which the PW corresponds based on the destination MAC address,
and forwards the packet to Spoke-PE 2.