Mayur's BLOG

TO OPEN OR CLOSE PORTS:

Before using commands for opening the port please make sure the specific port is already opened and what is the use of that port.

you can verify the port with

netstat -nap | grep :

1.you can open OR block TCp port with following syntax

iptables -A INPUT -p tcp –dport -j ACCEPT
iptables -A INPUT -p tcp –dport -j DROP - to block the port

2. You can open UDP port with

iptables -A INPUT -p udp –sport -j ACCEPT
iptables -A INPUT -p udp –sport -j DROP - to block the port

after that

3 service iptables save

TO allow or block IPs:

iptables -A INPUT -s <> -j ACCEPT
iptables -A INPUT -s <> -j DROP - to block the IP

Make sure to save IPtables if you did changes in IPtables


Usefull Options
Either long or short options are allowed.
--append -A chain Append to chain
--delete -D chain Delete matching rule from chain
--delete -D chain rulenum
Delete rule rulenum (1 = first) from chain
--insert -I chain [rulenum]
Insert in chain as rulenum (default 1=first)
--replace -R chain rulenum
Replace rule rulenum (1 = first) in chain
--list -L [chain] List the rules in a chain or all chains
--flush -F [chain] Delete all rules in chain or all chains
--zero -Z [chain] Zero counters in chain or all chains
--new -N chain Create a new user-defined chain
--delete-chain
-X [chain] Delete a user-defined chain
--policy -P chain target
Change policy on chain to target

service iptables save - To save IPtables
service iptables restart - To restart the IPtables firewall.

Enjoy