X emulation problem

sanjibgupta · 02-13-2006, 12:44 AM

Hi
I have a network which is divided into 2 parts. The 1st part machine has the (i) Netwok (ii) ROUTER (iii)Firewall Linux Rehat enterprise 2.1 server(eth0) (iv) Brodcast.
The second part has (i) eth1 port the Firewall server (ii) Proxy server Linux Rehat enterprise 2.1 server(eth0)
(iii) eth1 port of Proxy serverwhich masquaders the local IP(local address 192.168.20.1)(iv) The rest of the local network.

I generally logon to different Linux server and SUN SGI machine in my local network using X emulation from Windows PC using XDCMP (port 1777) and it runs fine.

But for some days i had a problem with Leased line connecting my 1st part of the network to the external internet. I couldnot logon to servers of internal(local) network during that time using X emulation though i was being able to telnet or ftp to those server.

Again I am able to do X emulation when my leased line is up now.

What might be problem? Please help me so i can even do a X emulation when my internet is down

Thanks
Sanjib Gupta

jschiwal · 02-13-2006, 02:39 AM

Code:

Internet --- Router --- RH Firewall----Proxy (NAT) --------------- Sun (xdcmp)
                          |                            |
     Broadcast(DMZ)- - - - |                            |------ Windows ( You are here! )
                          |                            |
     Server (DMZ)----------|                             |------ Linux Server ( xdcmp )
                                                       |
                                                       | ------- Other hosts
    ^              ^                                           ^       ^
   Internet IP Network Address                         (192.168.20.0 Network Address)

Are you saying that when the Internet <-> Router connection is broken, your windows machine can't log on to the Sun or Linux Machine, even though they are on the same subnet on the local (192.168.20.xxx) network?

The X Display Manager Protocol uses port 177 udp/tcp. Make sure both udp and tcp traffic gets through your windows/Sun/Linux host firewalls. (You said 1777).

I don't see how an internet disruption would effect the X windows traffic at all. Since the protocol isn't secure, and your site does have an internet connection, you may consider using SSH or TightVNC instead. You can enable X window forwarding in ssh and have the application window display on your Windows host. This is a different way of working, then logging into an X windows session, but one thing you can do is have one program on the screen that is running on the Sun Machine, and have another that is running on the Linux Machine.

You could try running traceroute on both targets for port 177. I hope that the traffic isn't taking some strange route instead of directly to those hosts.
--- --- --- ---
I'm sorry that I'm not an expert in XDCMP. Something made me think that you might be suffering from a man in the middle attack. Perhaps others can chime in and tell me how I am nuts! That would actually make me feel better, for your sake. ( I'm not tring to be alarmist. I just finished Mitnick's new book, and I'm seeing hackers around every corner! )

_______

I just had a thought. Check if the Linux and Sun computers are in the windows hosts file. If not, it may be going to another machine to resolve a the Sun and Linux hostnames. Maybe something isn't working correctly when the internet connection is down. Does your windows x-server have a log file. That may indicate what is going on also.