Delayed telnet login

[aunixguru]

I have a new problem with a sco system.

Until recently users were able to telnet in from another subnet just fine.

Now there is a 1-2 minute delay in getting the login prompt.

As far as I can tell , nothing has changed on the server or the network.

I have tried putting the ip of a machine on the other subnet in the host file and telnetting into the sco box from it. It did not fix the problem. Still a significant delay.

Anyone have any ideas of what the problem might be?

 

[pcunix]

From

http://pcunix.com/SCOFAQ/scotec4.html#telnetslow

Telnet/FTP is very slow to connect


If you are seeing a login but it takes a long time for the password prompt to appear after logging in, see User login hangs for many seconds before password prompt comes up (SCO 5.0.5 and 5.0.6 ):

http://pcunix.com/SCOFAQ/scotec6.html#slowlogin

Otherwise:

Slow telnet or ftp connections are often caused by the server wanting to do a reverse DNS lookup to find out who is connecting. If you aren't running DNS, you can fix this just by listing all the machines in /etc/hosts. Note that you don't have to be accurate about the names: I often use the ip adress with "_" substituted for the "."'s, like "host_192_168_2_3" and so on. A simple script:

#!/bin/ksh
x=1
while [ $x -lt 255 ]
do
echo "192.168.2.$x host_$x"
x=$((x + 1 ))
done >> /etc/hosts

Understand that being slow to give up on name resolution is an annoyance on small networks and a Good Thing on large networks. Systems that give up quickly work well on small networks, but don't get the information they should have on larger nets.


Tony Lawrence
SCO Unix/Linux Resources

http://pcunix.com

tony@pcunix.com

 

[jcsalfer]

Tony,

I've always assumed this was a reverse DNS lookup issue, but you mention "If you aren't running DNS, you can fix this just by listing all the machines in /etc/hosts."

The only time I've seen this issue come up is when /etc/resolv.conf is present and the machines are not in the hosts file. In which case I add them.

Isn't there a way to configure the system so it won't attempt a reverse DNS lookup if the address is not public?
John.

 

[pcunix]

Not that I'm aware of, no. Add the local machines to /etc/hosts as suggested is the simplest way. The other way of course is to setup your own local DNS server for everything.

Tony Lawrence
SCO Unix/Linux Resources

http://pcunix.com

tony@pcunix.com