Junos® OS Ethernet Interfaces Configuration ... - Juniper Networks

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OS 12.3 Ethernet Interfaces Configuration Guide
happening, the ICL designated forwarder should be elected between MC-LAG peers
and traffic received on an ICL could be forwarded to the active-active MC-LAG client
by the designated forwarder only.
Figure 7: Loop Caused by the ICL Links
N3
MCL3 ICL1 ICL2
MCL2
ge-0/0/0.0
MAC Address Management
94
ICL3
N1 N2
Active Active
MCL1
ge-1/0/0.0
5. When received from an ICL, traffic should not be forwarded to the core-facing client
link connection between two provider edge (PE) devices (C-Link) if the peer chassis's
(where the traffic is coming from) C-Link is UP.
If an MC-LAG is configured to be active-active, upstream and downstream traffic could
go through different MC-LAG network devices. Since the media access control address
(MAC address) is learned only on one of the MC-LAG network devices, the reverse
direction's traffic could be going through the other MC-LAG network and flooded
unnecessarily. Also, a single-homed client's MAC address is only learned on the MC-LAG
network device it is attached to. If a client attached to the peer MC-LAG network needs
to communicate with that single-homed client, then traffic would be flooded on the peer
MC-LAG network device. To avoid unnecessary flooding, whenever a MAC address is
learned on one of the MC-LAG network devices, it gets replicated to the peer MC-LAG
network device. The following conditions should be applied when MAC address replication
is performed:
• MAC addresses learned on a MC-LAG of one MC-LAG network device should be
replicated as learned on the same MC-LAG of the peer MC-LAG network device.
• MAC addresses learned on single-homed customer edge (CE) clients of one MC-LAG
network device should be replicated as learned on ICL-PL interface of the peer MC-LAG
network device.
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