Hello all.
We have a Redhat 7.3 machine running an odd OS extension called RealNG from IMS (essentially a multi-user DOS emulation layer). It allows access using its own terminal program for Windows called NGTerm. As far as we know, all it needs is port 160 to be open on the server.
When we test on a local machine, it works just fine and we get a DOS session, as expected. However, when trying to connect from a branch office (with port 160 open through the firewall), there seems to be a little handshaking and then they stop talking. Here's a tcpdump on the failing system:
Code:
[root@localhost root]# tcpdump host 129.100.101.100 and 10.119.100.100
tcpdump: listening on eth0
10:34:02.757677 10.119.100.100.2243 > 129.100.101.100.160: S 1266685911:1266685911(0) win 16384 <mss 1460,nop,nop,sackOK> (DF)
10:34:02.758998 129.100.101.100.160 > 10.119.100.100.2243: S 3526807905:3526807905(0) ack 1266685912 win 5840 <mss 1460,nop,nop,sack OK>(DF)
10:34:02.767588 10.119.100.100.2243 > 129.100.101.100.160: . ack 1 win 17520(DF)
10:34:02.767926 10.119.100.100.2243 > 129.100.101.100.160: P 1:2(1) ack 1 win 17520 (DF)
10:34:02.767975 129.100.101.100.160 > 10.119.100.100.2243: . ack 2 win 5840(DF)
10:34:02.768925 129.100.101.100.160 > 10.119.100.100.2243: R 1:1(0) ack 2 win 5840 (DF) <---- FAILS HERE
6 packets received by filter
0 packets dropped by kernel
If anyone can make any suggestions it would be highly appreciated. In the meantime, I have asked the technician to carry out a similar TCP dump on the working (local) pair of boxes to see what is supposed to come next in the sequence.
Thanks!
Simon Brindley