Do I configure port filtering and port forwarding with the same interface on simpler home-office routers?

Posted on 2011-05-04
Last Modified: 2012-05-11
I'm not a networking guy, by any stretch, but I will occasionally remote into the office Cisco ASA 5505 firewall and do some simple configuration.  With the Cisco, if you want to open a port and then configuring port forwarding, it's a two-step process.  

1. Open the port in the firewall.
2. Configure port forwarding for the port.

I was configuring a D-Link yesterday and it appeared that the port filtering and port forwarding was combined into one interface  Does that seem right?
Question by:jdana
    LVL 35

    Accepted Solution

    Keep in mind that ASAs are far more granular (regarding configuration) then D-Links (more home use than professional).
    Most home routers/firewalls do this in one step: if you forward a port, it has to be open.
    LVL 3

    Assisted Solution

    With the Cisco ASA depending on whether or not you are using static nat, policy nats, or if you only have one single outside IP address it could be a multi step process. First to create a Static Nat and second create an access-list. With a policy nat those two things are done at the same time giving the illusion of a 2 step process however opening the port/port forwarding is step 2 and creating the NAT is step 1.

    Port Forwarding and Port Filtering are generally separate.  Using Port filtering if I remember correctly is to block the use of a protocol except to a specific IP address or vice versa. Example there are some firewall rules that implemented by default on high end firewalls such not allowing private ip addresses to pass from the outside interface.

    Author Closing Comment

    Thanks guys.  Perfect.

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