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I have five machines: 10.0.0.5, 10.0.0.6, 10.0.0.7, 10.0.0.8, and 192.168.0.4.

The 10.x.x.x (DMZ) machines are all VMs (with IIS) running under 2008R2 Hyper-V. 192.168.0.4 is my workstation running Windows 7 Professional.

From a firewall/routing standpoint, the DMZ machines connect (eventually) to a Cisco ASA via a LocalDirector 430 (yes, it's an old and screwy setup.) The 192.168.0.4 machine connects to the ASA via the rest of the internal network.

Pings from 10.0.0.5 to 10.0.0.7&8 fail, and vice-versa. Pings from 10.0.0.6 to all machines in question succeed, and vice-versa. Pings from 192.168.0.4 (and a couple of other workstations on the same network) to all other machines mentioned succeed.


I've checked the following:

  • Firewall logs (no entries shown indicating any blocking, and ACLs for the four DMZ machines are in fact defined from a single group.)

  • Firewall changes (no changes within the past 2+ days, which is when this started happening.)

  • Windows Updates: At worst, they were pushed to the machines via patch management applications but not applied yet.

  • MAC address collisions (we've run into issues where Hyper-V servers stomped on each other's dynamic MACs.)

  • State of VMs shared by the host of 10.0.0.5; no problems there, which implies that the network controller in the VM host is fine.

  • Restarting the LocalDirector (old pieces of gear like restarts... as long as they come back up.)

  • Clearing the ARP cache on the ASA, before I realized that it's obviously right SOMEHOW since I was able to ping the machine from various other places.

  • VLAN status: All is as it should be - and from prior experience, if it wasn't, 10.0.0.5 wouldn't be able to talk to 10.0.0.6.

  • Restarting 10.0.0.5, 7, and 8 (two simultaneous failures? Why not!)

  • Various back and forth connections to port 80 (since all the DMZ machines run IIS;) these mirror the pings for success/failure.

  • A ping from another DMZ machine, a linux box, to 10.0.0.5; this also failed. I'm honestly not sure if this told me anything new, now that I type it.

  • Virus scan status; this shouldn't have caused this issue, but I was running out of ideas at this point.

What am I missing in this whole mess? Why can't 10.0.0.5 be reached by random other DMZ machines? This was working fine (as evidenced by logs) as of yesterday evening. It feels like the solution should be simple here, but this has everyone I've asked stumped.

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1 Answer 1

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So, the final solution to this was removing the Hyper-V network adapter in the Hyper-V Manager settings, re-adding it, and reconfiguring it with the appropriate IP address, etc.

I still don't know why this worked when a simple restart wouldn't, but it knocked something loose - suddenly all the machines can talk to each other again. Hopefully this weird problem (and the answer to it) helps someone else.

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