UNIX for Dummies Questions & Answers

I have users with laptops who may telnet from the local network one minute and then connect remotely a short time later from a different IP address.

This causes a problem as the UnixWare 7.1.1 server appears to try to resolve the remote machine name (via our primary DNS server) to the IP address that it connected from on it's previous connection. Since the IP address is different, it refuses the telnet session.

Is there a way to keep this from happening? Does it have anything to do with arp? I've used "arp -a", but I don't see anything relevant to the machine name/ip there.

Thanks in advance for any help you may be able to provide.

it seems your unixware is configure with tcpwrapper check /etc/hosts.allow and /etc/hosts.deny for any rule to confirm if this is the case.

if this is the case you may want to edit /etc/hosts.allow with and put this entry
telnetd: conecting_ip_address

Note
connecting_ip_address is your ipaddress you connectiong from.

if the above did not solve your problem you might want to use
hosts file before DNS resolution. just put an entry in your hosts file so that it uses your hosts file to do resolution.

I'm close to getting this resolved, thanks to your initial response, Hassan2.

I checked the man page on tcpd, which reports the following:

When looking up the client host name corresponding to an IP address, tcpd verifies the name that is returned by the DNS server by comparing it with the host name and address that are returned when the name is used to look up the corresponding IP address. This is know as a ``double reverse lookup''. If any discrepancy is detected, tcpd concludes that it is dealing with a host that is pretending to have someone else's host name.

The supplied version of tcpd was compiled with PARANOID defined, so that it will drop the connection in case of a host name/address mismatch.

Is it possible to edit hosts.allow with a valid subnet (or LIST of valid subnets) rather than each individual IP address?

yes you can put an entry of subnet in hosts.allow

like

telnetd: 171.65.0.0/255.255.0.0
or
telnetd: 171.65.30.0/255.255.255.0

Thanks, Hassan2...

Problem resolved!