topic Re: Telnet hangs through firewall in Operating System - HP-UX

Telnet hangs through firewall

Gavin Stewart — Tue, 19 Oct 2004 10:46:23 GMT

Hi,

I'm trying to install a Data Protector client from a server outside a firewall to 4 servers behind a firewall. Port 5555 has been opened by our network team who promise me all servers have the same firewall rules.

I can push a client out to these 3 servers, but the 4th just hangs when I try to install the client.

Also, if I do a "telnet hostname 5555" to this problem server, it connects but hangs. All other servers connect and then are "closed by foreign host" after about 10 seconds.

Can anyone think of a reason for this?

I thought it might be NFS related, but I stopped NFS and the problem persisted. Plus, ALL 4 servers have NFS running.

Any help would be greatly apreciated. Many thanks, Gavin.

Re: Telnet hangs through firewall

Simon Hargrave — Tue, 19 Oct 2004 10:48:59 GMT

If it connects then hangs, that implys a problem with the server itself.

What happens if you "telnet localhost 5555" from the server in question?

Re: Telnet hangs through firewall

Gavin Stewart — Tue, 19 Oct 2004 10:52:22 GMT

If I connect to the localhost from this server it connects fine (doesn't hang).

If I telnet to this problem server from another server behind the firewall it connects fine - this would probably suggest it's not a server issue!?

The problem only seems to be from a server outside the FW to this server behind the FW.

Thanks,

Gavin

Re: Telnet hangs through firewall

Mark Greene_1 — Tue, 19 Oct 2004 10:52:44 GMT

While telnet makes the initial connection based on the port provided (or port 23 as default), the connection back to the client is done on a random port number over 1000.

Also, if you've changed /etc/services to point telnetd to 5555, have you hup'd inet to pick-up the change?

mark

Re: Telnet hangs through firewall

Simon Hargrave — Tue, 19 Oct 2004 10:57:18 GMT

In that case I suggest that your network team haven't setup exactly the same rules.

Suggest you slap them with a wet fish and ask them to try again ;P

I'm assuming you can perform normal telnet to this server through the firewall no problem, and therefore that the routing tables are all present and correct?

Re: Telnet hangs through firewall

Gavin Stewart — Tue, 19 Oct 2004 11:02:02 GMT

Simon - I'm with you.

It doesn't appear to be a server issue as we can telnet to it from other servers behind the FW.

Normal telnet is not enabled through the firewall - only through port 5555.

Thanks.