Figure 36: Network Port Egress Packet Format And Flooding - Alcatel-Lucent 7750 SR OS Service Manual

Service router - mobile gateway

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VPLS Packet Walkthrough

c. The destination MAC address in the packet is looked up in the FIB table for the VPLS in-

d. If the destination MAC address has already been learned by PE-Router-A, an existing entry

e. PE-Router-A chooses a transport LSP to send the customer packets to PE-Router-C. The

table that associates the MAC address to the service access point (SAP) on which it was

stance. There are two possibilities: either the destination MAC address has already been

learned (known MAC address) or the destination MAC address is not yet learned (unknown

MAC address).

For a Known MAC Address

in the FIB table identifies the far-end PE-Router and the service VC-label (inner label) to

be used before sending the packet to far-end PE-Router-C.

customer packet is sent on this LSP once the IEEE 802.1Q tag is stripped and the service

VC-label (inner label) and the transport label (outer label) are added to the packet.

For an Unknown MAC Address

If the destination MAC address has not been learned, PE-Router-A will flood the packet to

both PE-Router-B and PE-Router-C that are participating in the service by using the VC-

labels that each PE-Router previously signaled for the VPLS instance. Note that the packet

is not sent to PE-Router-D since this VPLS service does not exist on that PE-Router.

Pre-assigned and

signaled by PE 'C'

Apply VC and

Tunnel Labels

Figure 4: Network Port Egress Packet Format and Flooding

IP/MPLS NETWORK

Pre-assigned and

signaled by PE 'B'

7750 SR OS Services Guide