What firewall are you using? If its ipchains, you can add a entry like so:<br>
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ipchains -A input -j ACCEPT -p tcp -d xxx.xxx.xxx.xxx 21<br>
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Where xxx.xxx.xxx.xxx is your IP address for the interface you are wanting to connect to.<br>
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There are a lot more options you can use also if you want to get really paranoid.<br>
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IPChains is the only firewall software I know, so if its ipfwadm, hopefully someone else can help...