Tightening up outgoing traffic

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On Tuesday 15 October 2002 3:32 pm, Dan Searle wrote:

> > I keep getting "domainname can not be found.  Please check the name and
> > try again" from my browser.  This only happens for new web sites (i.e.,
> > Yahoo works fine).  As this seems somewhat like a DNS issue, I tried
> > adding this:
> >
> > iptables -A OUTPUT -p tcp --destination-port nameserver -j ACCEPT
> >
> > but it didn't work.  Any ideas?  Thanks.
>
> iptables -A OUTPUT -p tcp --dport domain -j ACCEPT
> iptables -A OUTPUT -p udp --dport domain -j ACCEPT
>
> You want to use the service name "domain", not "nameserver",

In my version of /etc/services those are synonymous - 'domain' is the primary 
name of the service, and 'nameserver' is listed as an alias.

> also I think
> domain lookups use the udp protocol also. (Don't quote me on that one :-)

General rule for DNS is:

Client lookup on server uses UDP
Server to server transfers use TCP

Antony.

-- 

Documentation is like sex:
when it's good, it's very very good;
when it's bad, it's still better than nothing.



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