10.04 server not responding to some SSH requests

[vortmax]

I have a fresh install of ubuntu 10.04 server. The machine is sitting behind a NAT firewall. If I am logged into a machine on the local network (or the firewall), I can ssh into the machine just fine. If I put a port forward rule in the firewall and try to ssh into the machine from the outside, I can't get in.

Using tcpdump I have confirmed that the ssh packets are being forwarded correctly to the machine, but the machine never replies back.

As further testing, I started sshd in debug mode (bound to port 2222), and tcpdump watching for traffic on that port. If I ssh to the machine from a machine on the local network, I can see the traffic passing both ways in tcpdump and sshd starts dumping a lot of info. When I try it from outside the network, I see the packets coming into the machine in tcpdump, but sshd just sits there at "Server listening on :: port 2222".

I have another identical server that is working without a problem. What could be doing this?

[vortmax]

well it looks like posting the question on the internet solved the problem...

I rebooted the machine (which I had done several times) without changing anything, and this time when it came up, it started working.

[Hyp0tez]

ROFL

The magic of Internet fixed it then