Linux IPTables: How to Add Firewall Rules (With Allow SSH Example)

“This article explains how to add iptables firewall rules using
the “iptables -A” (append) command.

“”-A” is for append. If it makes it easier for you to remember
“-A” as add-rule (instead of append-rule), it is OK. But, keep in
mind that “-A” adds the rule at the end of the chain.

“Again, it is very important to remember that -A adds the rule
at the end.

“Typically the last rule will be to drop all packets. If you
already have a rule to drop all packets, and if you try to use “-A”
from the command-line to create new rule, you will end-up adding
the new rule after the current “drop all packets” rule, which will
make your new rule pretty much useless.”

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