Identifying physical port on server to port in VMware

Posted on 2016-07-28
Last Modified: 2016-11-22
Hello Experts - I need to move one of the four network cables from an ESX host to a different switch to get Websense working.  The NICs are labeled 1-4 on the Dell ESX host but in VMware they show up as vmnic0 through vmnic3.  I want to assume that port one on the ESX server matches vmnic0 in VMware but figured I'd check here before taking any chances since I need to make sure I don't interrupt any services.  Is there a reliable way I can be sure before I start pulling cables?
Question by:danbrown_
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LVL 10

Expert Comment

by:Richardson Porto
ID: 41733445
You can use CDP or LLDP (depending of your switch vendor) to see where which vmnic is connected. Take a look at the following KB article to see where to get that information:

Author Comment

ID: 41733454
I'm using HP2920 switches so no CDP.  I'm not familiar with LLDP and didn't see any reference to that in the link, did I miss it?
LVL 10

Expert Comment

by:Richardson Porto
ID: 41733467
Since you have a HP switch, I believe that LLDP is enabled by default on switch, but LLDP on vSphere side will only be available if you have Distributed Switch. The following blog post shows how to enable LLDP on distributed switch:
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LVL 120
ID: 41733470
you should be able to use show mac address on HP switches.

which will show you the MAC Address, or use SNMP and PRTG or Observium, which will map ALL MAC addresses to all ports on your switches for FREE!

Author Comment

ID: 41733558
Hmm, I thought this was going to be dead simple!  So I'm on the HP switch and when I run a show mac-address I do see quite a few but not the mac for the port I'm looking for.  I know it's plugged in there for sure.  I saw a few articles that say to run a port scan on the network but the way Websense works in my case is a port mirror for the port where the router is connected.  The NIC is configured without an IP address on the Websense server so a port scan does nothing here.  Is there a command on the HP I can run that will force it to revel the mac of a device connected to a specific port?
LVL 120
ID: 41733583
does this "device" with an IP Address, have a MAC Address ?

if it has no IP Address, and IS NOT sending traffic, it will not hit the switch!

Author Comment

ID: 41733596
It does have a mac but no IP, I found it using the vcenter client:

The Websense VM it is connected to has two NICs assisgned.  One is on the primary network shared with the other servers and the other is (supposed to be) plugged in to a port on the switch which mirrors the port where my router is connected.  This NIC on the server side has no IP address configured (IPv4 and IPv6 are disabled).  I have one of the ESX physical NICs dedicated to the task and just need to be sure I'm moving the right cable over.
LVL 120

Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 41733608
okay, I see what's happening here, if no traffic is coming from that mac address 14:18:77:62:67:5f, it will not show.

if the VM is just attached to a vSwitch, again it will not show....

but why don't you just quickly create a management network on that vSwitch/Nic, temp IP Address, ping it from workstation, and then get the mac address, and work out physical port?

then remove the management network.

Author Closing Comment

ID: 41733616
Thanks Andrew, I was able to confirm I had the right port this way.

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