no reverse DNS causing connectivity problems

[Jeffrey Goldberg]

[mailed and posted]

On Jun 9, 2008, at 8:57 PM, Jake Evans wrote:

> I've had a few people complain that when they telnet/ssh/ftp/web to  
> our server, it's slow... I've traced the problem to them having no  
> reverse on their IPs.

You should configure your servers to not do the reverse lookup.  Not  
resolving is certainly the default for Apache.  For sshd, set UseDNS  
to "no" in /etc/ssh/sshd_config.  As for telnet and ftp, I don't know  
where that might be configured.

Of course I don't know your needs and situation, but some people might  
consider it a reasonable policy to disallow ssh and telnet (and  
certainly mail) from hosts that don't have proper PTR records.

-j


-- 
Jeffrey Goldberg                        http://www.goldmark.org/jeff/