I have one sun Solaris computer running Sun Solaris 8 OS, on same LAN others computers are also connected which are running operating system MS Windows 2000 professional, but not in same subnet. All computers are connected to Internet.

My question is that:
Is there any way that I can connect to my Solaris Machine from Windows 2000 professional and can run GUI program of Sun Solaris?

I can do this with help of XManager, but only in same subnet. What about same thing in one LAN but in different subnet? Or Via Internet?

Given that it works when on the same subnet, is there some router filtering or a firewall in play?

Try the command "route" from the Windows 2000 Boxes. You can put both subnets together with it. But this only works, when you do not have a Gateway configured in your Solaris Box.

This is what I get one on my subnet when I applied route print command.

C:\>route print
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x1000003 ...00 06 5b 7c 80 85 ...... 3Com EtherLink PCI
===========================================================================
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.5.100.1 10.5.100.120 1
10.5.100.0 255.255.255.0 10.5.100.120 10.5.100.120 1
10.5.100.120 255.255.255.255 127.0.0.1 127.0.0.1 1
10.255.255.255 255.255.255.255 10.5.100.120 10.5.100.120 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
224.0.0.0 224.0.0.0 10.5.100.120 10.5.100.120 1
255.255.255.255 255.255.255.255 10.5.100.120 10.5.100.120 1
Default Gateway: 10.5.100.1
===========================================================================
Persistent Routes:
None