I have a linode for running vulnerable websites and services for testing. I have set iptables to require use of a proxy linode to access the linode.

Will this restrict all access to the linode to the one IP address?

iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -d 127.0.0.0/8 -j REJECT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -j ACCEPT

iptables -A INPUT -s 173.255.192.138 -j ACCEPT

iptables -A INPUT -j DROP
iptables -A FORWARD -j DROP

That depends on what rules existed in the INPUT chain before those commands are executed. The "iptables -A" command appends the rule to the given chain, so rules that existed earlier will be processed first. Remember that iptables rules are processed sequentially, so order matters.

Run "iptables -L -n" to get a complete dump of all chains and post the result here.

Oh, and you should always test using "nmap <ip_here>" from both 173.255.192.138 and an external IP to ensure it actually works.

I'm using nmap from another linode, and it seems to think it is down. Sounds like it's working.