Hi everybody,
I have recently had an interesting experience and was wondering if someone has had same or similar issues.
Basically my setup is this:
SuperHub 3 in modem mode
Own router running on a virtual machine (dd-wrt) on a Vmware esxi host with a dedicated NIC and a static MAC address on the VM
This has been running without any issues for the last several years, but recently I decided to tweak and streamline my environment a bit further. As I have two identical esxi hosts running in a DRS cluster, it was only logical to ensure that the router VM could be automatically migrated to any of the hosts. So to implement this feature, I created a separate VLAN on my Netgear managed switch with three ports only, one connected to the SuperHub and two connected to dedicated NICs on each host.
So far so good, the setup is working, the router VM could be migrated to any host without any noticeable service interruption.
The issue I had happened during a migration which coincided with a heavy traffic to the shared storage for the hosts, which lead to the router VM stalling. During the revival process i did a WAN DHCP address release and attempted a renewal, which proved to be unsuccessful.
So starting to troubleshoot, I noticed that if the VM is connected directly to the SuperHub, the DHCP process will work. Then if the link is transferred through the switch, it will continue working, also it will renew the IP address, but if I attempt release and then renew, it will not work.
Further investigation showed that I had jumbo frames enabled across the switch, which also has been the case for the modem VLAN. The hosts NICs have been set to MTU 1500, also I believe this is the setup of the SuperHub (no way to check or change)
Currently I have set the MTU for the VLAN to 1500, but have not had a chance to test the setup and see if this was the problem, but just wondering if someone here is familiar with the specifics or has experienced such a problem before? It will save me some wireshark packet sniffing in order to try and figure out what the issue was...