DavidRing.ie

Somtimes you may have encountered an issue where a VNX/VMAX front-end port gets cabled to the wrong MDS Switch Port that you had designed for and in fact the port description that was applied to the MDS Port is incorrect. In this case it is invaluable to have a command to verify the VNX/VMAX port connected to the MDS. There are many situations where this command would be useful; for example you may not have the ability to do a physical check as the DC is remote and you need to ensure the interface description that you are assigning the MDS FC Port is correct and resulting zoning configurations are accurate. Confirming these connections remotely through a command on the MDS is very benneficial during these types of situations. Else you may end up zoning to ports you did not design for.

VMAX Example

So lets take an example: the design and expectation here is to have the VMAX Port 9G:1 connected to MDS FC Interface 2/37 and the interface was given the relevant description:

From this result we can see that the port was labeled as per design as VMAX 9G:1. Now we need to confirm this is the actual port connected to FC2/37.

To analyse the connectivity of a specific interface we first need to retrieve the FCID for this port:
show interface fc2/37

Now that we know the FCID is 0x010440, we can run our magic Cisco cmd to verify which VMAX FA Port is actually connected to the MDS Port FC2/37 :

show fcns database fcid 0x010440 detail vsan 10

Note: FCNS = Fibre Channel Name Server.

From the output we can confirm that there is a problem; the expected VMAX Port was 9G1 but in fact 7G1 is the VMAX port patched to FC2/37 (SYMMETRIX::000195701570::SAF- 7gB::FC::5876_229). Thus either we update the description of the interface or have the correct VMAX Port patched.

To modify the description:
interface fc2/37
Switchport description VMAX20K-7g1
no shutdown

VNX Example

Interface FC1/25 as per design is connected to Service Processor ‘A2’ front-end port 2:

Running show interface fc1/25 in order to confirm port description and retrieve the FCID:

Now that we know the FCID is 0x010500, we can query the FCNS database for details of what is connected at the other end of FC1/25:
show fcns database fcid 0x010500 detail vsan 10

From the output we can confirm the correct port is connected from the VNX.

Another method of confirming the correct port is connected, is by gathering the WWPN from the VNX/VMAX port and then running the show flogi database interface fc 1/25 command on the MDS:

Reverse Lookup
From the VNX we can run a “naviseccli -h SP_IP port -list”:

From the output we can see that SPA_6(Logical Port) is connected to the MDS interface WWN 20:19:54:7f:ee:e2:9e:f8.
Given this information we can lookup the Interface Port number by issuing: show fcs database | include 20:19:54:7f:ee:e2:9e:f8

Thus we can conclude from this output that the VNX Physcial Port SPA:2_2 is connected to MDS Port FC1/25.

Note: If we want to look up the details of all the switch ports on the MDS this is the command:
show fcns database detail