OT: Telenet to terminal server dropping -ubuntu 10 driving me

Has anyone seen this telnet issue?
I am connected to my 2511 terminal server using telnet from my laptop. It
will work for something 2 or 3 hours (not timed) perfectly.
then all of sudden ping from my laptop to Terminal server still works but
all my telnet windows hung , see below .

DSL/WIFI-RTR------wifi----LAPTOP
|
|-----10/100 LANwire--------Terminal Server---to lab gears

both laptop and terminal servers are in the same subnet no firewall in
between etc. other PC from my WLAN can telnet okay, its just the my laptop.

Radioactive_at_frog ~/Desktop $ telnet 50.1.3.2
Trying 50.1.3.2...
Connected to 50.1.3.2.
Escape character is '^]'.

At the same time I have another router which I telnet from my laptop shows
the same issue "escape character blah" and nothing happens after that. I
dont get to put user/pass.

So it's just not the terminal server.

Tried a little bit digging on it and the fix was "enable" disable my
wireless connection. i.e. on my IBM R61p press Fn key + F5.
I can telnet after that and access lab normally.

resetting TCP stack --> /etc/init.d/networking restart didn't fix it.

No firewall configured on this. So I was wondering

frog Desktop # tcpdump -ni wlan0 | grep 50.1.3
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlan0, link-type EN10MB (Ethernet), capture size 65535 bytes

12:00:54.313282 IP 50.1.3.15.53851 > 50.1.3.2.23: Flags [P.], seq
2208563960:2208563987, ack 1599023550, win 5840, length 27
12:00:55.982996 IP 50.1.3.15.60803 > 50.1.3.2.23: Flags [S], seq 382968090,
win 5840, options [mss 1460,sackOK,TS val 4156193 ecr 0,nop,wscale 6],
length 0
12:00:56.004516 IP 50.1.3.2.23 > 50.1.3.15.60803: Flags [S.], seq
3537695090, ack 382968091, win 4128, options [mss 1460], length 0
12:00:56.004551 IP 50.1.3.15.60803 > 50.1.3.2.23: Flags [.], ack 1, win
5840, length 0
12:00:56.004675 IP 50.1.3.15.60803 > 50.1.3.2.23: Flags [P.], seq 1:28, ack
1, win 5840, length 27
12:00:56.213642 IP 50.1.3.2.23 > 50.1.3.15.60803: Flags [.], ack 28, win
4101, length 0

.15 = my laptop IP
.2 = Terminal srv IP

see above tcpdump , laptop (.15) keep sending ack but never get syn.

It's just my lapotp that is playing up. SSH works but not the telnet.

Anyone have seen above?
I have upgraded kernel to the latest but still seeing this happening. I can
access everything else but not the telnet.
i can access the internet etc okay on my laptop. ssh to other switch in the
same subnet is okay. changed the cable.

Blogs and organic groups at http://www.ccie.net
Received on Sun Jan 23 2011 - 12:08:51 ART