SCO Unix ® FAQ section

TCP/IP and NFS FAQ

Telnet/FTP is very slow to connect

Slow telnet or ftp connections (Unix and Linux) 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
 
	

Almost ALL machines want to know who is connecting to them - Unix, Linux, Windows, whatever. If their DNS doesn't give a quick answer, anything trying to connect will be delayed.

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.

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

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