Network Connection Issues with Hyper-V Host and VM's

A few of our clients started to have strange network connection issues starting a few months ago at random times. I wanted to see if anyone is having the same issue or could shed some light into what is going on. We have a consistent setup among our client this is only happening to a few. Thanks!

Problem:

Either both the Hyper-V host and the VM's will lose network connection (internet and LAN communication) or just some of the VM's.

Setup:

- All servers are Dell's with 2 Broadcom Network Adapters. Network Driver/firmware and Windows updates are up to date with latest.
- All servers are using Teamed Adapters in Switch Independent mode and dynamic load balancing
- HyperV host shares vSwitch for ManagementOS and VM’s
- Basic out of the box Hyper-V setup and not clustering

Behavior:

-      Some or all VM’s will lose network communication with other servers, desktops and the internet
-      The network adapters on the Host and VM’s don’t display any issues right away and eventually will say no internet access
-      Hyper-V host is unable to ping default gateway, the VM’s, or any public IP address. Team and both NIC’s do not display any issues are show as up. At times, I am still able to initial a remote connection to the HV host even though the HV host can’t communicate to the internet and can’t ping the gateway.

Temporary resolution:

I am able to resolve the issue by disabling one of the network adapters and re-enabling. Network communication comes back.

Troubleshooting:

The only thing I can see in the event log in the following Event

Log Name:      System
Source:        Microsoft-Windows-MsLbfoSysEvtProvider
Date:          7/14/2015 9:54:55 AM
Event ID:      16945
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      HV-01
Description:
MAC conflict: A port on the virtual switch has the same MAC as one of the underlying team members on Team Nic Microsoft Network Adapter Multiplexor Driver
Event Xml:

Running a Get-NetAdapater shows that there are the same MAC addresses however, other servers that are working fine show the same. I manually set all of the MAC addresses to something different but still get the event log entry and still have the same issue.

Name                      InterfaceDescription                    ifIndex Status       MacAddress             LinkSpeed
----                      --------------------                    ------- ------       ----------             ---------
NIC1                      Broadcom NetXtreme Gigabit Ethernet #2       13 Up           F8-BC-12-4D-35-AE         1 Gbps
vEthernet (SWITCH-01) Hyper-V Virtual Ethernet Adapter #2          21 Up           F8-BC-12-4D-35-AE         10 Gbps
Hyper-V Team              Microsoft Network Adapter Multiplexo...      18 Up           F8-BC-12-4D-35-AE         2 Gbps
NIC2                      Broadcom NetXtreme Gigabit Ethernet          12 Up           F8-BC-12-4D-35-B0         1 Gbps
dougholdAsked:
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Philip ElderTechnical Architect - HA/Compute/StorageCommented:
Turn VMQ off for all Broadcom Gigabit ports. This is a known issue with Broadcom Gigabit NICs.

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dougholdAuthor Commented:
Thanks! This is exactly what the issue was.
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