Multi-Hop Pw - HP HSR6800 Configuration Manual

2. When receiving the packet, PE 1 determines which VSI the packet belongs to by the VLAN tag
and, based on the destination MAC address of the packet, tags the packet with the multiplex
distinguishing flag (MPLS label) for the PW. Then, it forwards the packet.
3. Upon receiving the packet from the PW, PE 1 determines to which VSI the packet belongs by
the multiplex distinguishing flag (MPLS label) and, based on the destination MAC address of
the packet, labels the packet with the VLAN tag. Then, it forwards the packet through the QinQ
tunnel to MTU, which in turn forwards the packet to the CE.
For packets to be exchanged between CE 1 and CE 2, MTU can forward them directly without PE 1
because it holds the bridging function by itself. For the first data packet with an unknown destination
MAC address or a broadcast packet, MTU broadcasts the packet to CE 2 through the bridging
function and, at the same time, forwards it through the QinQ tunnel to PE 1, which replicates the
packet and sends a copy to each peer CE.
PW redundancy
The network design with a single PW between a UPE and an NPE has a distinct drawback: once the
PW experiences a failure, all VPNs connected to the aggregate device lose connectivity. The
H-VPLS with LSP access provides redundant links for PW backup. The primary PW link is used.
When the primary link fails, the backup link takes over the VPN services.
Figure 57 PW redundancy for H-VPLS with LSP access
CE 1
CE 2
(Backup link)
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 primary link failure.
•
The LDP session between the peers of the primary PW goes down, and the PW is deleted as a
result.

Multi-hop PW

A PW cannot be setup directly between two PEs when:
•
The two PEs are in different Autonomous Systems (ASs), where they cannot establish a
singling connection.
•
The two PEs use different PW signaling protocols.
In such cases, you can establish multiple continuous PW segments that function as a single PW,
called a "multi-hop PW," a virtual connection between the two PEs.
NPE 1
N-PW
U-PW
UPE
N-PW
N-PW
U-PW
NPE 2
NPE 3
CE 3
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