While checking fex links, we got the " Identity-Mismatch" error as shown below in "sh int fex" output:
Nexus-5k-1# sh int fex-fabric
Fabric Fabric Fex FEX
Fex Port Port State Uplink Model Serial
---------------------------------------------------------------
103 Eth1/17 Active 1 N2K-C2248TP-1GE JAX1122AAA
103 Eth1/18 Active 2 N2K-C2248TP-1GE JAX1122AAA
103 Eth1/19 Active 3 N2K-C2248TP-1GE JAX1122AAA
103 Eth1/20 Active 4 N2K-C2248TP-1GE JAX1122AAA
105 Eth1/23 Active 1 N2K-C2248TP-1GE MLX1122BBB
105 Eth1/24 Active 2 N2K-C2248TP-1GE MLX1122BBB
105 Eth1/25 Identity-Mismatch 4 N2K-C2248TP-1GE PQR3344DDD <<<Notice this
105 Eth1/26 Active 4 N2K-C2248TP-1GE MLX1122BBB
Nexus-5k-2# sh int fex-fabric
Fabric Fabric Fex FEX
Fex Port Port State Uplink Model Serial
---------------------------------------------------------------
102 Eth1/17 Active 1 N2K-C2248TP-1GE LMN2244CCC
102 Eth1/18 Active 2 N2K-C2248TP-1GE LMN2244CCC
102 Eth1/19 Active 3 N2K-C2248TP-1GE LMN2244CCC
102 Eth1/20 Active 4 N2K-C2248TP-1GE LMN2244CCC
104 Eth1/23 Active 1 N2K-C2248TP-1GE PQR3344DDD
104 Eth1/24 Active 2 N2K-C2248TP-1GE PQR3344DDD
104 Eth1/25 Active 3 N2K-C2248TP-1GE PQR3344DDD
104 Eth1/26 Identity-Mismatch 3 N2K-C2248TP-1GE MLX1122BBB <<<Notice this
Basically this error is related to incorrect cabling..
As we know that a nexus 2k switch or FEX is connected to its parent Nexus 5k over fex links.
One Fex (2k) can be dual homed to two Nexus 5k switches. and when a nexus 2k is connected to Nexus 5k, a unique fex associate number is assigned to that particular 2k to identify it uniquely.
So, i had four nexus 2k switches whose serial numbers are JAX1122AAA,MLX1122BBB, PQR3344DDD and LMN2244CCC. JAX1122AAA and ,MLX1122BBB are FEX switches for Nexus5k1. and PQR3344DDD and LMN2244CCC are part of Nexus-5k-2. JAX1122AAA has been given FEX associate number 103 and MLX1122BBB has been given 105,LMN2244CCC is assigned 102 and PQR3344DDD is assigned 104. Each fex is connected to its parent switch via 4 fex links.
Idealy, all 4 fex links which are under same FEX ASSOCIATE NUMBER should be going to same 2k,however, one of our onsite engineer incorrectly cabled one of the fex link from 103 on Nexus-5k-1 to another 2k which was part of FEX number 104 on Nexus-5k-2 and we started getting identity mismatch. As you can see in above output,under FEX 105 on Nexus-5k-1, the Eth1/25 is showing PQR3344DDD serial number,however, all other interfaces showing MLX1122BBB and vice versa on Nexus-5k-2 for Eth1/26.
In order to verify cabling and make sure right fex or 2k is connected to correct parent 5k switch with respective to its FEX associate number, we can use "show interface fex-fabric" command and verify the same using serial number that all are correct switches.
once the cable were swapped, we started getting right serial number for Eth1/25.
Nexus-5k-1# sh int fex-fabric
Fabric Fabric Fex FEX
Fex Port Port State Uplink Model Serial
---------------------------------------------------------------
103 Eth1/17 Active 1 N2K-C2248TP-1GE JAX1122AAA
103 Eth1/18 Active 2 N2K-C2248TP-1GE JAX1122AAA
103 Eth1/19 Active 3 N2K-C2248TP-1GE JAX1122AAA
103 Eth1/20 Active 4 N2K-C2248TP-1GE JAX1122AAA
105 Eth1/23 Active 1 N2K-C2248TP-1GE MLX1122BBB
105 Eth1/24 Active 2 N2K-C2248TP-1GE MLX1122BBB
105 Eth1/25 Active 3 N2K-C2248TP-1GE MLX1122BBB ---->>>>Correct now
105 Eth1/26 Active 4 N2K-C2248TP-1GE MLX1122BBB
Was helpful. met with similer issue and this helped
ReplyDeleteJust had the same issue and came across this post - very useful - thanks.
ReplyDeleteHad this issue today and a google search got me to this page. Thanks for the post.
ReplyDeleteThank you..I am new in Nexus and had job where this seems to be exact issue.
ReplyDeletehope that was solved :-)
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