Unblock IP in iptables

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If you are using fail2ban or similar tools, they block IP addresses, that they think are attacking them. fail2ban blocks IP addresses eg after a certain number of invalid login attempts.

However, sometimes you accidentally lock yourself out. In this case, access the server via a different IP (or the emergency console) and remove the IP from iptables:

Unblock fail2ban

You can take a look at a numbered list of blocked ips:

iptables -L f2b-sshd -n -v --line-numbers

It may look like this:

Chain f2b-sshd (1 references)
 num   pkts bytes target     prot opt in     out     source               destination
 1       18  2160 DROP       all  --  *      *
 2       54  5184 DROP       all  --  *      *

You can now remove certain lines with the command:

iptables -D f2b-sshd {i}

Keep in mind: after you removed a line, the following lines will move up so the indexes will change. So either remove from “the bottom up” (by descending line number) or recheck the list after every removal.