[CentOS] named is up but does not respond to queries

[Leonard Isham]

On 8/24/05, Les Mikesell <lesmikesell at gmail.com> wrote:
> On Wed, 2005-08-24 at 10:34, Arun K. Khan wrote:
> > CentOS 4.1/bind-9.2.4-2.
> >
> > I have named serving as a cache DNS server plus SOA for a local intranet
> > zone.
> >
> > The problem I am encountering - over a period of time it stops
> > responding to queries.
> 
> >         (from 192.168.1.150)
> >         $ host www.yahoo.com 192.168.1.21
> >         ;; connection timed out; no servers could be reached
> >
> >         # nmapfe of 192.168.1.21  (from 192.168.1.150)
> >         (The 1208 ports scanned but not shown below are in state:
> >         closed)
> >         PORT      STATE SERVICE
> >         22/tcp    open  ssh
> >         25/tcp    open  smtp
> >         53/tcp    open  domain
> >
> >         (ssh'd into named server using IP# 192.168.1.21)
> >         # service named status
> >         rndc: recv failed: operation canceled
> 
> It looks like it can't reach the root servers.  It has a private
> address  - could you have a problem with your NAT gateway to the
> internet?   How about your local firewalling on 53/udp to let
> the responses back?
> 

For DNS servers 53/tcp is required as well. UDP handles most requests
but when the amount of data is great enough it uses TCP.  IIRC yahoo
returns quite a few.
-- 
Leonard Isham, CISSP 
Ostendo non ostento.