I'm having a situation with Hyper-V that I really need some help with. We recently added a 4th physical host to our Hyper-V cluster. It was working fine until this last weekend when some things got rebooted, now one of the VLANs isn't reachable. The main culprit is a SQL server that is clustered, and running on VLAN 3. When I ping the IP address within VLAN 3, I can reach it from any of the others. Let's call it IP 1. When I ping from the AD machine inside VLAN 3, it's reachable. When I connect to the SQL Server on IP 1 from one of the two cluster members, I can connect to the database.
When I go to one of the servers in VLAN 2 that needs to talk to it and try to connect, I can't. I moved one of the IIS Servers that's on the same host from VLAN 1 into VLAN 3 and re-iped it, and when I did it was able to connect and return data from the SQL Cluster, I then moved it into VLAN 2 and re-iped again it would not connect. I've tried moving that same IIS Server onto one of the previous hosts, and am having resource issues where the VM won't start.
I'd love to hear some suggestions on other things I can test at this point. I don't have physical access to the hosts, but I have contact with those who do. We've checked a few different things and just can not figure out what might be happening or the next steps. I don't have SCVMM running, and am hesitant to activate it and potentially cause a production issue as I understand I would have to add the whole cluster at one time. I've thought about rebuilding the SQL clusters in VLAN 3, but they validate, and show that things should be working, and when moving into that VLAN everything works.
I've also verified the DNS and Subnet masking and both are accurate and should work. Additionally, other machines in VLAN 3 are reachable, such as the AD server that is there. Some production machines are in the same VLAN 3 as well and working fine.