[ubuntu] Wildcard iptables delete

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http://ubuntuforums.org – Hello. I'm brand new to Linux, but a long time Windows administrator, so I understand the concepts, not the syntax. I've stumbled through setting up Ubuntu Server as a NAT server. It's working great now. My goal is to map public IPs to private IPs. However, I want to change them often through an automated fashion (SSH remote call). So, I want to run commands that will remove the previous rule and add a new rule, or update the existing rule. For example, the original rule may be something like: iptables -t nat -I PREROUTING -d -j DNAT --to-destination iptables -t nat -I POSTROUTING -s -j SNAT --to-source The issue I'm running into is finding out how to delete the previous entry before adding a new one. For example, let's say that should now map to (instead of .5). Is there a wildcard option for the delete rule so that I don't need to know the original destination IP? i.e. iptables -t nat -D PREROUTING -d -j DNAT --to-destination [+] Or, would it make sense to create a script that traverses all rules, gets the existing rule, and then deletes it? Of course my next issue would be that I don't know any Linux scripting so it's hard to know where to start. (HowTos)