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Nexus 7010 / Fex MAC Learning Issue /// rare Issue

Hi!,

We have a rare behavior on a couple of Nexus 7010. We have connected a new server with two interfaces configured as active/standby to a couple of nexus FEX interfaces.


Something like this.
-----------
Server||-----> NIC1 (active) ---> Interface 101/1/6 on Fex 101 --> Nexus #1 7010 L2 Context
Server||-----> NIC2 (standby) ---> Interface 104/1/6 on Fex 104 --> Nexus #2 7010 L2 Context
______

The configuration on these interfaces are just "switchport access vlan 56" but the server had connectivity issues (some people can reach the ip and some other not).

Looking for a problem with the server we just find out this.

If you look for the MAC address on the Nexus #1, the MAC address is being learned on Eth101/1/6

3T-NX7-S1-L2#
3T-NX7-S1-L2# sh mac address-table | grep 0894.ef10.1344
* 56 0894.ef10.1344 dynamic 0 F F Eth101/1/6

BUT if you look for the same MAC address on the Nexus #2, the Mac address is also learned on the interface Ethernet 101/1/6 but this interfaces does not exist on this Nexus!!

3T-NX7-S2-L2#
3T-NX7-S2-L2# sh mac address-table | grep 0894.ef10.1344
* 56 0894.ef10.1344 dynamic 0 F F Eth101/1/6

3T-NX7-S2-L2# sh mac address-table | include 101/1/6
* 56 0894.ef10.1344 dynamic 30 F F Eth101/1/6
3T-NX7-S2-L2# sh int ethernet 101/1/6
^
% Incomplete command at '^' marker.
3T-NX7-S2-L2# sh fex
FEX FEX FEX FEX
Number Description State Model Serial
------------------------------------------------------------------------
103 FEX-2248TP-1GE Online N2K-C2248TP-1GE FOX1724G9BN
104 FEX-2248TP-1GE Online N2K-C2248TP-1GE FOX1724G99C
3T-NX7-S2-L2#

The connection between the two Nexus 7010 is with Fabric Path, the Vlan 56 is also a Fabric Path Vlan.

I have no explanation for this behavior. 

Any idea will be appreciated.

1 REPLY 1
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Cisco Employee

Hi,

Could you please provide the output for

show system internal l2fm l2dbg macdb address 0894.ef10.1344

Take it from both Nexus, that command will show us which interface inserted the Mac address in  the Nexus.

Regards!

-Enrique

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