We have two network switches, a POE switch (SwitchA) to power our phones / users computers and a non-POE switch (SwitchB for the rest network.)

Each switch is setup to do port mirroring to support our VoIP recording system. SwitchA does port mirroring on specific ports if we need to record a user. SwitchB mirrors one port to monitor our work at home users (Internet comes in from managed router, to switch, back out to our firewall.) These two port mirroring setups feed into one vmware vSphere 4.1 server, it has four total physical cards. The other two NICs feed into an unmanaged switch for connecting to the rest of the network.

Once into the vSphere server all network ports go into a vSwitch, and then one of the servers (Windows 2008 R2) sniffs them out and does its thing.

Everything is working fine and dandy from SwitchB. But on SwitchA we only receive one side of the VoIP packets (going out to the phone, nothing coming in from the phone).

Troubleshooting steps I have taken so far:

• I hooked up my laptop to the monitor port on SwitchB and I see both sides of the packets.
• I swapped which network interface is plugged into the monitor port on SwitchA.

Because everything feeds into one vSwitch / vNetwork and both sides of the conversation arrive just fine from SwitchB I believe everything is configured correctly on the vSphere server/guest.

What could be causing one way packets to arrive on my guest machine from only one interface, but not the other? Could a bad cable be causing the problems from SwitchB?