[nsp] dns forwarding

[Eric Pylko]

You're right, but if you set your DNS server to 192.168.0.255 that would be
a broadcast.  The router _should_ forward that to whatever is configured in
the ip-helper command.  Whether the DNS server will respond to it is an
entirely different question.

Now that I think of it, you might have to do a "no ip directed-broadcast" on
the interface also to make sure the broadcast gets into the router.

-Eric

--
Eric Pylko			eric at infinitenetworks.us
CCIE #5827			(585) 747-2446


-----Original Message-----
From: Christian Kuhtz [mailto:christian.kuhtz at bellsouth.com] 
Sent: Wednesday, July 07, 2004 1:39 PM
To: Eric Pylko; 'Kristofer Sigurdsson'; 'Roger'
Cc: cisco-nsp
Subject: Re: [nsp] dns forwarding


Maybe I'm missing something here, but a resolver query to, say, 192.168.0.1
isn't a broadcast, guys ;).. Forget the ip helper.

A dedicated NAT/PAT rule is more like it if at all.

Or using a Dynamic Host Configuration Protocol server for actual dynamic
configuration ;)... And do away with a hack.

On 7/7/04 1:30 PM, "Eric Pylko" <eric at infinitenetworks.us> wrote:

> The ip helper-address command forwards all sorts of broadcasts.  By
default
> it does DHCP and a bunch of others (tftp, dns, time (port 37), tacacs,
bootp
> client, bootp server, nb name service, and nb datagram service).  These
are
> all UDP ports that it forwards.
> 
> If you want to disable those (or enable others) you can do with with "no
ip
> forward-protocol" or "ip forward-protocol" as needed.
> 
> -Eric
> 
> --
> Eric Pylko   eric at infinitenetworks.us
> CCIE #5827   (585) 747-2446
> 
> 
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Kristofer
Sigurdsson
> Sent: Wednesday, July 07, 2004 1:01 PM
> To: Roger
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [nsp] dns forwarding
> 
> Roger, Wed, Jul 07, 2004 at 11:48:11AM -0500 :
>> Richard Danielli wrote:
>> 
>>> Roger,
>>> 
>>> If you only have to satisfy client requests, you might consider looking
>>> to the ip-helper address command in IOS.
>>> 
>>> 
>> 
>> Tried that..  Didn't work..  I put the helper address on the internal
>> interface and pointed the help-address to the dns server.
>> 
>> I tried a dns query on the ip of the router and it returned nothing.
>> From my understanding the helper-address forwards udp broadcasts - ie
>> for dhcp/bootp a dns query is a udp unicast.
> 
> The helper-address directs BOOTP/DHCP IIRC - not broadcasts in general.


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