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Cisco 877 with NAT – can I forward TWO external ports to ONE internal port?

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    jimwillsher
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    #143425

    Hi all,

    Cisco 877, 12.4(24)T. Single public IP, NAT to 192.168.1.x

    I’m running a mailserver insider the LAN, and I connect to it from my laptop to send emails when inside and also when outside. When I’m travelling I sometimes encounter ISPs who are blocking port 25 to anything but their own mailserver, so I need to connect to a different port in order to send to my ow mailserver.

    Ideally, what I want is for inbound traffic on port 25 to be forwarded to my mailserver, as normal. BUT I also want traffic on port 12345 to be forwarded to port 25 on the mailserver.

    Using this rule is fine:

    Code:
    ip nat inside source static tcp 192.168.1.50 25 interface Dialer0 25

    for port 25. But when I then do this:

    Code:
    ip nat inside source static tcp 192.168.1.50 25 interface Dialer0 12345

    my existing port 25 rule gets replaced. What I want is something like this:

    Code:
    ip nat inside source static tcp 192.168.1.50 25 interface Dialer0 25
    ip nat inside source static tcp 192.168.1.50 25 interface Dialer0 12345

    or

    Code:
    ip nat inside source static tcp 192.168.1.50 25 interface Dialer0 25, 12345

    etc.

    Can anyone suggest a solution? I’d rather not change the mailserver to listen on two ports as it’s a bit messy.

    Many thanks.

    Jim

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