Configure port forwarding with iptables on Slackware

1. Goal

Publish an internal service with NAT and clear PREROUTING and FORWARD rules.

2. Files and components involved

/proc/sys/net/ipv4/ip_forward
iptables
/etc/rc.d/rc.local

3. Operational flow

echo 1 > /proc/sys/net/ipv4/ip_forward
add DNAT and FORWARD rules
save firewall script

4. Operational verification

iptables -t nat -L -n -v
iptables -L FORWARD -n -v
test from external client

5. Practical notes

Apply network changes from a local console or with an emergency session ready, so you do not lose SSH access.

Every network change should have a rollback path ready: a second console, KVM access, or a temporary command to remove.

Quick checklist

[ ] Backup or copy of the existing configuration completed
[ ] Files and commands updated as expected
[ ] Local test completed successfully
[ ] Logs or final output verified
[ ] Rollback procedure documented

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