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N-Series Unicast-as-Multicast Sample Configuration


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Article ID: 10906

Products
Matrix N-Series DFE

Changes
Installed Load Sharing server software (e.g. NLB), or similar application that uses the same MAC address on multiple network adapters.
Configured SNMP Traps (5390).
Globally and port enabled the MAC Move trap type ('set movedaddrtrap...').

Symptoms
Network latency and communication timeouts.
Seeing certain MAC addresses ingressing on more than a single port per MAC.<165>Aug 15 17:35:13 10.1.3.200 AddrNtfy[2]MAC: 00-03-BA-E4-30-FD moved to port
ge.2.55, FID 700
<165>Aug 15 17:35:52 10.1.3.200 AddrNtfy[3]MAC: 00-03-BA-E4-30-FD moved to port
ge.3.8, FID 700
<165>Aug 15 17:35:58 10.1.3.200 Last message repeated 1 time
<165>Aug 15 17:36:43 10.1.3.200 AddrNtfy[2]MAC: 00-03-BA-E4-30-FD moved to port
ge.2.55, FID 700
<165>Aug 15 17:36:37 10.1.3.200 Last message repeated 1 time
<165>Aug 15 17:37:00 10.1.3.200 AddrNtfy[3]MAC: 00-03-BA-E4-30-FD moved to port
ge.3.8, FID 700
<165>Aug 15 17:37:15 10.1.3.200 Last message repeated 1 time
<165>Aug 15 17:37:54 10.1.3.200 Last message repeated 1 time
<165>Aug 15 17:40:13 10.1.3.200 AddrNtfy[2]MAC: 00-03-BA-E4-30-FD moved to port
ge.2.55, FID 700
<165>Aug 15 17:40:52 10.1.3.200 AddrNtfy[3]MAC: 00-03-BA-E4-30-FD moved to port
ge.3.8, FID 700[/code]
Cause
The CPU is constantly relearning and reprogramming the Source MACs local to the ports. The key effect is to potentially direct response traffic to the "wrong" port - that is, to an adapter that is not receptive to it.

Investigation shows that the multi-port MAC source is an expected and desirable element of the software deployed in the network, but that an ability of the switch to forward response unicast traffic to more than one destination port (overriding standard transparent learning) should prevent the existing forwarding confusion and stop the messages.

Solution
Enable the 'set mac unicast as multicast' feature to treat unicast flows as both learned and forwarded as multicast.

Here is the configuration that should resolve the messages shown above:set mac unicast-as-multicast enable
set mac multicast 00-03-ba-e4-30-fd 700 ge.2.55 append
set mac multicast 00-03-ba-e4-30-fd 700 ge.3.8 append[/code]
Note that this has no effect on receiving a specific source MAC address on multiple ports, but rather allows any response traffic to be forwarded back to those same ports. Since this static configuration overrides transparent Source Address Table (SAT) learning, the messages will stop as well.

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