SCO Unix...

ME dugan at
Tue Aug 7 12:15:31 PDT 2001

On Tue, 7 Aug 2001, Christopher Wagner wrote:
> 1) When a user telnet's into the system, it connects but doesn't give
> any output for quite some time.  The length of time varies, sometimes
> can be up to 5 minutes or so.  Now, the catch is, when I telnet
> localhost on the box, it comes up instantly..  Or if I telnet from
> either our Ascend or Netopia routers, again, instantaneous, just like I
> would expect from a 10/100 network.  I haven't tried telnetting from the
> external network because opening telnet to the outside with a Unix box
> would be silly. :)  The internal network is IP masqueraded behind the
> routers, and the addresses for most of the internal computers are
> delivered by DHCP by our NT server <cringes away from the evil box>.
> Any ideas why this would be happening?

A guess:
The telnet daemon is attempting to privide a reverse lookup for the IP
address that is copnnecting, but a firewall rule, or improperly setup
DNS-lookup rule is blocking the process. When this happens, the request
for reverselookup may be blocking further connection data from passing
until the namelookup times out.

To test this:
Lookup an IP address of a remote machine from which you have present
shell access for telnet.
Add that IP address of that machine that has previously been having long 
waits for connections to the /etc/hosts file with a name
now try to telnet into the box from that remote machine with the IP
address just added to the /etc/hosts file. If you *now* get a zippy
response, then examine your DNS. Maybe you have a bad one, bad
/etc/resolv.conf poor rules for ourgoing requests for DNS, blocking for
incoming requests. lots of possible things for this...

There are other items that might be of issue, but I thought I would take a
stab at the most likely. (ex: tcp wrappers settings is not perfect and a
timeout is waiting and blocking.)

> 2) The Network Config app in SCOAdmin takes around 5 mins everytime I
> open it to read all the network configuration stuff.  Could this be
> related?

Yes, this is likely if it is also doing reverse lookup of the IP address
connecting for log files. Also could be an authentication scheme you might
be using. Try the top suggestion first.


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     Systems Department Operating Systems Analyst for the SSU Library

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