Hi all,
we are using linux debian guest on vmware ESX, and this linux guest is setup to be a router for other linux servers with iptables. Now the prolem is as follows: when we try to do scp of ftp file transfer from this linux guest to any other host, the transfer is working fine. But when we try to do a transfer from some other linux machine through the linux router (and through iptables) the connection is dropped as soon as the transfer starts. SSH connection from other linux machines through the linux router also drops if you try to less a large file with error "connection reset by peer".
I know that this sounds like MTU issue but all network cards have MTU set to 1500, and we tried iptables option clamp-mss-to-pmtu with no luck. iptables does not have any other entries other then masquerade on outgoing interface.
We are quite sure that this problem is somehow connected to ESX, because this is a new setup. Before this we had exactly the same setup but with router installed on phisycal machine. When we migrated this router to ESX, the problems started to apear. ESX network card is connected to the switch with trunk, and router's virtual network card is set to vlanXX.
Right before the connection is dropped, tcpdump shows a lot of "TCP dup ACK" packages, and on the other side "TCP ACKed lost segment". Any help is appreciated.
