Author: J. Patrick Narkinsky
Email: patrick@narkinsky.ml.org
Web Page: http://www.narkinsky.ml.org/
Date Submitted: Mon, Oct 12, 1998
Status: New Entry

Requester: Chris
Email: theking@seanet.com
Request Made: Tue, Apr 21, 1998

Releases: all
Platform: all
Category:  Networking and netcfg
Category Listing:  FTP, HTTP, and Telnet are all slow immeiately after initial connection.

Issue

I just Installed linux Redhat 4.2 Full Install 450 megs. What would 
cause the FTP server, Httpd, and Telnet Servers to have SLOW 
responce time when tring to login.? Sometimes it will take 5 mins 
before I even get a User Input responce, Ie. User Name, Password. 
The Httpd Server dose the same thing. Telnet Server Just sits 
there and looks dumb. Thanks for the help. Email to: 
theking@seanet.com 

Response

Almost invariably, the type of problems you describe are the 
result of an incomplete/incorrect reverse DNS setup. In other 
words, the machine which is trying to connect to you does not 
have a reverse DNS entry (or possibly has a reverse DNS entry and 
does not have a matching forward entry). I would recommend two 
possible solutions for this: first, try getting reverse DNS 
entries setup for the machines in question. Failing this, add 
entries for the machines you will be telnetting from to the 
/etc/hosts file. Most programs will use this file as an alternative 
to DNS. DNS is an internet protocol/database which allows the host 
names with which we are all familiar to be converted to IP 
addresses. Unfortunately, because of the structure of DNS it is 
impossible to use a single entry to the DNS for both forward 
(that is I have a hostname and need an IP address) and reverse (I 
have an IP address and want the hostname) entries. So, every 
properly configured machine on the internet should have two DNS: 
one for forward lookups and one for reverse. Very often, network 
managers are lazy and either do not setup reverse entries at all 
or only set them up for servers. THIS IS TOTALLY BOGUS AND 
INCORRECT AND WILL CAUSE ALL KINDS OF PROBLEMS. ALL INTERNET 
CONNECTED MACHINES SHOULD HAVE MATCHING FORWARD AND REVERSE DNS 
ENTRIES. Most Linux networking programs (including all of the 
three you mentioned) attempt to get a hostname for a machine when 
it connects. If this machine does not have a reverse DNS entry (or 
possible an entry in /etc/hosts) then this query will have to time 
out before the application can continue. Typically the timeout 
can take 30-60 seconds, and will result in exactly the kind of "slow 
connect performance" problem you are describing. Short form: make 
sure all your machines have reverse DNS entries. 

References

Man: named /usr/doc/HOWTO/DNS-HOWTO