XenServer 7.0 Mellanox
I’ve been working on an issue where a trunked vlan wasn’t working when tagged in XenServer. Now this server was in a pool of 4 nodes so tricky to diagnose as they were production VMs running on the system. This all started because client using the server only need one vlan presented and this was setup natively as if there only one network. Initially, I thought the network vlan have not been trunked correctly, but it turned out to be a driver issue with the 25GB Mellonx cards.
How to troubleshoot:
First you need to have the vlans trunked to your XenServer, then you need to see traffic on your interfaces.
Putty into your Xenserver, normally the pool Master.
Run xe pif-list to get a list of all your interfaces.
To check driver version use ethtool –i eth0 or what interface your Mellanox card is.
If your driver is 3.1-1 then you could have the same issue I was experiencing.
Run tcpdump -i <device> -w /<path to file> see https://support.citrix.com/article/CTX120869 for more info
You want to see you vlan interfaces has packets sent/received
Resolution:
The easiest way to have the drivers updated is to just upgrade XenServer from 7.0 to 7.2 which uses Mellanox driver 3.4-1 and this worked for us.