Cisco 877 Router open ports

Posted on 2011-10-14
Last Modified: 2012-06-27
I have recently installed a Cisco 877 router.

We now need to open a port for workstations on the lan to access AOL (port 5190) What is the best way to do this.

Also we are sending e-mail out from our exchange server to an smtp mail server on the web what is the best way to configure the router for this?

Thanks for your assistance.

Question by:Potts2002
    LVL 5

    Expert Comment

    Is the 877 performing NAT for you? Do you have dynamic VPN trafic?
    LVL 5

    Accepted Solution

    Lets assume NAT and no dynamic VPN

    ! where insideAdder is the actual ip address of your AOL server, like and
    ! OutsideAdder is your fixed IP address from your ISP - If it not fixed, this is more complex but doable
    ip nat inside source static tcp insideAdder OutsideAdder 5190

    ! Change FastEtnernet4 to the actual outside interface, the one that has the ip nat outside
    interface FastEthernet4
     description $FW_OUTSIDE$$ES_WAN$
     ip nat outside
    ! You may already have an access group for packets inbound, if so, then you will use that group
     ip access-group 112 in

    ! Note 112 matches the 112 in the access-group above and OutsideAddr is your external IP address again
    access-list 112 permit tcp any host OutsideAddr eq 5190

    LVL 10

    Assisted Solution

    I'm not sure if that's correct; that will block any other traffic including returning HTTP traffic for instance as the 877 doesn't have a stateful firewall embedded.

    When you say to allow workstations to allow AOL on port 5190, are connections coming into your network or outside your network?

    The best practice for outgoing email is to block ANY outgoing smtp traffic except for your exhcange server

    ip access-list in->out
    20 permit tcp host <exchange ip> any eq 25 log
    30 deny tcp any any eq 25 log
    40 permit ip any any

    int f4
    ip access-group in->out out

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