Figure 59: Network Port Egress Packet Format And Flooding - Alcatel-Lucent 7750 SR Manual

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2. Core Router Switching
a. All the core routers ('P' routers in IETF nomenclature) between PE-Router-A and PE-Rout-
3. PE-Router-C
a. PE-Router-C strips the transport label of the received packet to reveal the inner VC-label.
b. PE-Router-C learns the source MAC address in the packet and creates an entry in the FIB
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 been learned by PE-Router-C, an existing entry in the
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signaled by PE 'C'.
Tunnel
Label
Customer
Location A
Apply VC and
Tunnel Labels
Tunnel
Label
signaled by PE 'B'.

Figure 59: Network Port Egress Packet Format and Flooding

er-B and PE-Router-C are Label Switch Routers (LSRs) that switch the packet based on the
transport (outer) label of the packet until the packet arrives at far-end PE-Router. All core
routers are unaware that this traffic is associated with a VPLS service.
The VC-label identifies the VPLS service instance to which the packet belongs.
table that associates the MAC address to PE-Router-A and the VC-label that PE-Router-A
signaled it for the VPLS service .
stance. Again, there are two possibilities: either the destination MAC address has already
been learned (known MAC address) or the destination MAC address has not been learned
on the access side of PE-Router-C (unknown MAC address).
Known MAC address
FIB table identifies the local access port and the IEEE 802.1Q tag to be added before send-
ing the packet to customer Location-C. The egress Q tag may be different than the ingress
Q tag.
Pre-assigned and
VC
Dest
Src
Label X
MAC
MAC
PE A
IP/MPLS Network
B
VC
Dest
Src
Label Y
MAC
MAC
Pre-assigned and
(Figure
60)
Customer
Packet
PE C
B
B
PE B
Customer
Packet
OSSG203
7750 SR OS Services Guide

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