DNS forward

Discussion in 'Cisco' started by mboe, Nov 24, 2004.

  1. mboe

    mboe Guest

    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
     
    mboe, Nov 24, 2004
    #1
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  2. mboe

    Erik Freitag Guest

    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.
     
    Erik Freitag, Nov 24, 2004
    #2
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  3. mboe

    Ben Guest

    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"
     
    Ben, Nov 24, 2004
    #3
  4. mboe

    Erik Freitag Guest

    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".
     
    Erik Freitag, Nov 24, 2004
    #4
  5. mboe

    mboe Guest

    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
     
    mboe, Nov 25, 2004
    #5
  6. mboe

    Erik Freitag Guest

    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 ...
     
    Erik Freitag, Nov 25, 2004
    #6
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