problem involving NAT and PAT

Discussion in 'Cisco' started by Ionut, Jul 30, 2004.

  1. Ionut

    Ionut Guest

    I have a Cisco 2651 xm router with 2 interfaces. First, the external,
    mapped to the ip address allocated by the provider, corresponding to
    my domain, let's say www.x.com. The other one, internal, with an ip of
    10.1.1.1. My LAN has addressess in the pool 10.1.1.0/24. I have also
    an web server with ip 10.1.1.2.
    I use NAT on the router for the 10.1.1.0/24 to be able to access
    internet and it works fine. I also have a port forwarding rule to
    allow people from internet to visit my web site (www.x.com:80 is
    forwarded to 10.1.1.2:80) and it also works fine. The only problem is
    that I can't access the web server if I am in the LAN (address
    10.1.1.5 for example). If i try to open http://www.x.com/ it fails.
    But if I connect directly to the web server (open http://10.1.1.2/) it
    also works. I can put an alias in hosts.txt on my local computer or
    make an internal name server to tell me that www.x.com has the IP
    10.1.1.2 but is there a possibility to solve it obly with some
    configuration on the router?

    I know it has to make a double transformation to the packets (for
    example a packet originating from 10.1.1.5:2000 -> www.x.com:80 should
    be transformed by the router into a packet like www.x.com:60000 ->
    10.1.1.2:80 ) and I don't know if this is possible in the IOS
    Software.
     
    Ionut, Jul 30, 2004
    #1
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  2. Ionut

    PES Guest

    If you can do a one to one nat instead of a port address translation it will
    work if the dns server for www.x.com is on the outside. This is basically
    because if nat sees a one to one translation for an IP address that is in
    the translation table it will translate the dns response to the internal
    counterpart. In a port forwarding or pat scenario, this is not the case.

    "Ionut" <> wrote in message
    news:...
    > I have a Cisco 2651 xm router with 2 interfaces. First, the external,
    > mapped to the ip address allocated by the provider, corresponding to
    > my domain, let's say www.x.com. The other one, internal, with an ip of
    > 10.1.1.1. My LAN has addressess in the pool 10.1.1.0/24. I have also
    > an web server with ip 10.1.1.2.
    > I use NAT on the router for the 10.1.1.0/24 to be able to access
    > internet and it works fine. I also have a port forwarding rule to
    > allow people from internet to visit my web site (www.x.com:80 is
    > forwarded to 10.1.1.2:80) and it also works fine. The only problem is
    > that I can't access the web server if I am in the LAN (address
    > 10.1.1.5 for example). If i try to open http://www.x.com/ it fails.
    > But if I connect directly to the web server (open http://10.1.1.2/) it
    > also works. I can put an alias in hosts.txt on my local computer or
    > make an internal name server to tell me that www.x.com has the IP
    > 10.1.1.2 but is there a possibility to solve it obly with some
    > configuration on the router?
    >
    > I know it has to make a double transformation to the packets (for
    > example a packet originating from 10.1.1.5:2000 -> www.x.com:80 should
    > be transformed by the router into a packet like www.x.com:60000 ->
    > 10.1.1.2:80 ) and I don't know if this is possible in the IOS
    > Software.
     
    PES, Jul 31, 2004
    #2
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