netfilter Cheat Sheet

Syntax

nft list tables
nft list chains

nft add    <table|chain|rule> ...
nft list   <table|chain|rule> ...
nft flush  <table|chain|rule> ...
nft delete <table|chain|rule> ...

List rules with numbers

nft list ruleset -a

Check rules for syntax errors

nft --check -f /etc/nftables/sio-firewall.nft

Simple Example

Create new table and chain:

nft add table    inet table1
nft create chain inet table1 { type filter hook input priority 0\; }
nft add rule     inet table1 chain1 iif lo accept

Allow existing and outbind, as well as SSH

nft add rule     inet table1 chain1 ct state established,related accept
nft add rule     inet table1 chain1 tcp dport 22 ct state new accept

Default drop policy

nft add rule     inet table1 chain1 drop

Advanced

Inject rule at position

nft add rule inet table1 chain1 position <number> <rule>

Convert iptables to nftables

Check out iptables-translate

Debug rule changes

nft monitor               # Reports all rule changes live
nft monitor new tables
nft monitor destroy rules

SIO Firewall rules

/etc/nftables/sio-firewall.nft
/etc/sysconfig/nftables.conf          include "/etc/nftables/sio-firewall.nft"

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