Sam Pointer

I’ve been using a couple of nice shell aliases when working with ad-hoc iptables rules. You can spruce them up as a batch file, but they’re fine for me as a quick and dirty way to manipulate rules.

alias ips="/sbin/iptables --line-numbers -vn -L INPUT | grep -i"
alias ipd="/sbin/iptables -D INPUT"

That’s all there is to it. You can then interrogate almost any aspect of the default INPUT filter with:

ips icmp
ips 10.64.0
ips drop

to view all ICMP rules, any rules relating to the 10.64.0 subnet, or all rules that drop packets.

The way I use these together, and the reason that `ips` includes the –line-numbers argument, is that I like to add rules and then easily delete them with:

# ips 192
30       0     0 DROP       all  --  *      *       192.0.2.0/24         0.0.0.0/0
# ipd 30

using the rule number as an easier way of deleting the rule without having to conjour up a matching rule specification.