I recently deployed ProCurve 1800-24G switches in place of some older ProCurve 2424M switches in my network. However, I'm having a serious problem with the switch connected to the router. It seems, every night when our Windows 2008 R2 server (off site) runs a backup to a iSCSI target (on site) [facilitated through a PPTP tunnel] the LAN loses connectivity with the router. To clarify, there is only one router which is connected to the switch affected by this problem. The only way to resolve the issue is to either reboot the router or pull the ethernet cable that goes to the router and plug it back in.

During the outage, clients cannot receive DHCP requests, DNS requests, ping, or do anything else with the router in this state. Now, neither the switch or router are configured extensively and the issue only seems to have surfaced with the new switch in place. I have tried a number of things including replacing cables, rebooting and checking the switch configuration (it is literally as basic as you can get at this point-- flat LAN, no trunking). Interestingly, the router shows (accessed externally) no changes in configuration or status during this state but similarly cannot ping or access other hosts on the network.

This issue occurs in different stages of backup (ie, different amounts transferred). I've also dumped packets from the switch into WireShark but cannot seem to find any anomaly yet (I'm looking at packets around the time the issue appeared and at the time when I reset the NIC). Any suggestions for what to look for? Ideas on what could be causing this? I'm seeing some transmit/receive errors on the NIC from both the router and switch side but nothing serious when compared to the total packet counts. I'm seriously doubting hardware at this point, as I have tried another switch, different cables, and a different NIC on the router.