I have found posts that tell me destination host unreachable means the sender has no route to the destination, but when i bring up the destination it all of a sudden can ping and gets that route. A bit confusing.
It does mean that but perhaps not in the way you think in terms of "route".
Do you remember whether the destination host unreachable message was reported by the switch or not ?
If everything is in the same vlan then there is no actual routing to be done ie. it is all L2 and not L3.
So what it is telling you is that the server could not resolve the IP address to a mac address. If it has no mac address for the host it cannot put any packets on the wire so it reports destination host unreachable.
With a request timed out packets can be put on the wire and sent but there is no response obviously because the host is down. So it's almost as if the server has a mac address for the first few pings and then removes it from it's arp cache and then cannot send any more packets.
When you bring the host back up the server can then get the mac address through arp and your pings start working again.
What this has to do with the switch I'm not sure because it should not be involved. It's not about the switches mac address table because even if the mac address wasn't there that is at L2 so the switch should not generate any message. It should only generate the message if it was being asked to L3 switch the packet and it isn't.
It's probably too late to do any troubleshooting as you have moved it all into a different vlan and it is working.
I can't think of any obvious reason as to why it behaved like this but just thought I would explain some of the symptoms you were seeing.
If anything does occur I'll post back.
Jon
