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port routing/forwarding on cisco 1841 - routing for exchange email

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  • port routing/forwarding on cisco 1841 - routing for exchange email

    I Hope i have placed this in the correct forum.

    I am hoping that someone can assist me in this.

    Here is my situation. I am setting up an exchange 2007 server and am having some issues getting emails to it from the internet/external networks. I am trying to get the smtp port 25 to route thought the router to the email server on the internal network. internally can send and receive emails just fine. As of Friday we could send emails OUT to an external address, though today it seems to not be working. I have run all the diags from within exchange and it is working just fine. I have checked and double checked our DNS settings and can ping our email server domain from external and have it resolve to our external ip that is configured on the router.

    I have added routes in NAT to both TCP and udp(though nt sure i needed to do udp) and have even gone to set up ACL to try and force it that way. the NAT config caused no errors etc, but the ACL which was configured as perimit from external(any ip network) smtp port 25 to internal ip 192.168.2.51 smtp port 25. When i put this rule in place, i lose all ping contact with the server on that ip or its back up ip and even remote desktop to that server.

    can any one tell what i am missing? What i am doing wrong?

  • #2
    Re: port routing/forwarding on cisco 1841 - routing for exchange email

    well an update, the nat rules that i put in place did in fact cause some issues, caused the email server to be blocked from the inet completely, so upon removeing them it has access again, but the router is still not forwarding through smtp for port 25.

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    • #3
      Re: port routing/forwarding on cisco 1841 - routing for exchange email

      Hi,

      Have you tried using something like this?

      ip nat inside source static tcp <insert-internal-ip-address-here> 25 interface <external-interface> 25

      For example, I would use something like:

      ip nat inside source static tcp 192.168.1.10 25 interface Dialer0 25

      I use similiar rules on my Cisco 1841 to port forward through for RDP and HTTP traffic to my internal network.

      Good luck!

      Cheers,
      Matthew

      Comment


      • #4
        Re: port routing/forwarding on cisco 1841 - routing for exchange email

        [quote=matthewj;150769]Hi,

        Have you tried using something like this?

        ip nat inside source static tcp <insert-internal-ip-address-here> 25 interface <external-interface> 25

        For example, I would use something like:

        ip nat inside source static tcp 192.168.1.10 25 interface Dialer0 25

        I use similiar rules on my Cisco 1841 to port forward through for RDP and HTTP traffic to my internal network.
        "

        ip nat inside source static tcp <insert-internal-ip-address-here> interface <external-interface>

        works fine both directions.

        ip nat inside source static tcp <insert-internal-ip-address-here> interface <external-interface>

        According to my testing:

        ip nat inside source static tcp <insert-internal-ip-address-here> 25 <insert output allocated address for mail server> 25

        Works fine one directions and that is from outside but not from inside to inet. You have to put following to work both direction:

        ip nat inside source list 123 pool Mypool

        where Mypool has address allocated for your mail server. Same address from perhaps your ISP MX definition etc

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