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# 1  
Old 05-12-2008
Telnet Problem

I have a problem where on one unix machine I can telnet all IP addresses in the host file with no connection problem and another machine has recently started to have trouble connecting with the same host IP's on just some IP addresses where it had no trouble before. Have any ideas??
# 2  
Old 05-12-2008
Quote:
Originally Posted by tazzy
I have a problem where on one unix machine I can telnet all IP addresses in the host file with no connection problem and another machine has recently started to have trouble connecting with the same host IP's on just some IP addresses where it had no trouble before. Have any ideas??
maybe that server is installed with tcp wrapper.

In TCP wrapper you can specify which IP address is allowed to connect. Maybe the other host or PC using DHCP and the IP changed so previously he could get in but now couldn't.
# 3  
Old 05-12-2008
How would I check to see if tcp wrapper has been put in place or activated since we just recently started having this problem?
# 4  
Old 05-12-2008
Quote:
Originally Posted by tazzy
How would I check to see if tcp wrapper has been put in place or activated since we just recently started having this problem?
Search your server for a file called inetd.sec

find / -name inetd.sec -print

if you do find it back it up first before making any changes. You can edit this file on the fly there is no need for reboot or restarting any processes.

The other possibility is that the host trying to connect to the server does not have a route. to check you can do a netstat -rn

good luck
# 5  
Old 05-12-2008
TCP wrappers uses the /etc/hosts.deny file to control access. It will produce something in the system log when a connection was blocked.

It doesn't just go activate itself so I'd bet more on the random DHCP fluff theory.
# 6  
Old 05-12-2008
There is no inetd.sec on the system. Is it possible that a network card going bad would cause the server not to be able to telnet to certain IP addresses? Things were working fine a couple of weeks ago and now just on this one machine it is not allowing to telnet to certain addresses.
# 7  
Old 05-12-2008
Is there some sort of pattern to "certain addresses"? That would indicate a routing problem, perhaps external to the machine itself. Do other things besides telnet work? What about ping, traceroute, ssh?

Are you using DHCP? Did the machine's IP address change, like, for instance, not so coincidentally around the time the problems started?

Do you have working reverse DNS, and do the other machines possibly care whether or not you do? Is there anything else on their end which might be preventing the connections?
 

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