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DNS forward

 
 
mboe
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      11-24-2004
Hi,

I have a 1605R with IOS 12.3. I'm trying to use this machine to forward DNS
requests.
I mean, on a PC I use the 1605R as DNS server and the 1605R should resolve
this request on an outside DNS server and send the result back to the PC.
DNS works from the Router, but the PC doesn't get an answer back. Connection
PC to Router is fine.

Thanks
Michael


 
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Erik Freitag
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      11-24-2004
On Wed, 24 Nov 2004 01:03:02 +0100, mboe wrote:

> Hi,
>
> I have a 1605R with IOS 12.3. I'm trying to use this machine to forward DNS
> requests.
> I mean, on a PC I use the 1605R as DNS server and the 1605R should resolve
> this request on an outside DNS server and send the result back to the PC.
> DNS works from the Router, but the PC doesn't get an answer back. Connection
> PC to Router is fine.
>
> Thanks
> Michael



I assume you have set the "ip dns server" global command and that DNS
resolution works when you try it from the router (i.e. ping
www.cisco.com).

I've noticed that this feature works for 1700s, 2600s and
3600s, but does not seem to work for 7200s. Perhaps there's a problem with
1600s.


 
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Ben
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      11-24-2004
Erik Freitag wrote:
> On Wed, 24 Nov 2004 01:03:02 +0100, mboe wrote:
>
>
>>Hi,
>>
>>I have a 1605R with IOS 12.3. I'm trying to use this machine to forward DNS
>>requests.
>>I mean, on a PC I use the 1605R as DNS server and the 1605R should resolve
>>this request on an outside DNS server and send the result back to the PC.
>>DNS works from the Router, but the PC doesn't get an answer back. Connection
>>PC to Router is fine.
>>
>>Thanks
>>Michael

>
>
>
> I assume you have set the "ip dns server" global command and that DNS
> resolution works when you try it from the router (i.e. ping
> www.cisco.com).
>
> I've noticed that this feature works for 1700s, 2600s and
> 3600s, but does not seem to work for 7200s. Perhaps there's a problem with
> 1600s.
>
>

It works fine, but I believe the command is "ip name-server x.x.x.x"
 
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Erik Freitag
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      11-24-2004
On Wed, 24 Nov 2004 21:34:11 +0000, Ben wrote:

> Erik Freitag wrote:
>> On Wed, 24 Nov 2004 01:03:02 +0100, mboe wrote:
>>
>>
>>>Hi,
>>>
>>>I have a 1605R with IOS 12.3. I'm trying to use this machine to forward DNS
>>>requests.
>>>I mean, on a PC I use the 1605R as DNS server and the 1605R should resolve
>>>this request on an outside DNS server and send the result back to the PC.
>>>DNS works from the Router, but the PC doesn't get an answer back. Connection
>>>PC to Router is fine.
>>>
>>>Thanks
>>>Michael

>>
>>
>>
>> I assume you have set the "ip dns server" global command and that DNS
>> resolution works when you try it from the router (i.e. ping
>> www.cisco.com).
>>
>> I've noticed that this feature works for 1700s, 2600s and
>> 3600s, but does not seem to work for 7200s. Perhaps there's a problem with
>> 1600s.
>>
>>

> It works fine, but I believe the command is "ip name-server x.x.x.x"


That's different, or rather, you might need that too. That's why I asked
if name resolution was working on the router. I believe the original
poster was asking about using an IOS router as a cacheing DNS server,
since he says he is using the router as a DNS for his PC. This is
supported in 12.3, except for the possible problem I've noted on 7206 and
now 1605 routers.

If your router receives a list of DNS servers from a DHCP server, then
you only need "ip dns server" in the configuration. If it does not, then
you need to tell it where to go to do lookups using "ip name-server
A.B.C.D".


 
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mboe
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      11-25-2004
hi,

the command i needed was "ip dns server", but it seems not to be included in
the 1605.
I tried it with a 3620 and it works fine.

Thanks for the hint
Michael


 
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Erik Freitag
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      11-25-2004
On Thu, 25 Nov 2004 03:18:01 +0100, mboe wrote:

> hi,
>
> the command i needed was "ip dns server", but it seems not to be included in
> the 1605.
> I tried it with a 3620 and it works fine.
>
> Thanks for the hint
> Michael


There's virtually no documentation on this command. You can find a mention
but not much more under "ip dns spoofing" in the 12.3 docs. If you're
logging you may see some times when the DNS server is overloaded (and
dropping requests). This is probably not a good way to provide DNS
services in a production environment right now ...
 
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