And bingo! I totally spaced on the fact that the MAC pool would be the same on the two clusters. I changed the pool range (Configure->MAC Address Pools for anyone interested) on the 4.1 cluster and things are looking good again. Thank you, this was driving me nuts! On 2017-04-11 05:22 AM, users-request@ovirt.org wrote:

Message: 1 Date: Mon, 10 Apr 2017 21:07:44 -0400 From: Jeff Bailey <bailey@cs.kent.edu> To: users@ovirt.org Subject: Re: [ovirt-users] More 4.1 Networking Questions Message-ID: <31d1821c-9172-5a62-4f7d-b43fa4608025@cs.kent.edu> Content-Type: text/plain; charset=windows-1252; format=flowed

On 4/10/2017 6:59 AM, Charles Tassell wrote:

...

Ah, spoke to soon. 30 seconds later the network went down with IPv6 disabled. So it does appear to be a host forwarding problem, not a VM problem. I have an oVirt 4.0 cluster on the same network that doesn't have these issues, so it must be a configuration issue somewhere. Here is a dump of my ip config on the host:

The same L2 network? Using the same range of MAC addresses? [snip]