Potential routing issue???

[Adam Noble]

Hi all,

We have a strange issue and I wonder if somebody could confirm my thinking. We have a customer from outside of our firewall connecting to our server. When he attempts to telnet (yes I know) he simply gets no output and when he attempts to ssh to the server he gets a login prompt. Once he enters his username it simply hangs forever. This is not an ssh/telnet or login issue as I can connect perfectly well on the same subnet.

I have noticed that although our server is sitting outside of our firewall requests to certain IP addresses are routed back via our firewall address. I cannot for example do a traceroute to the customers server even tho he is simply sitting on the internet. Would you even get a login prompt (for ssh) if it was unable to send packets back to the customer from this server. My thinking is he can connect to the server however no packets can be routed back to him? Any ideas?

Cheers

[Jonathan Fife · Accepted solution]

The ssh client should be receiving *some* data back from the server before it presents a login. The initialization of a TCP connection requires that both the client and server acknowledge each other. That would make a routing issue unlikely.

I suspect that this might instead be a DNS issue. If you do an nslookup on the IP address your server sees him connecting from, does it resolve quickly?