I am facing a problem to open port 25 with iptables on my CentOS machine. I checked the connection by 'nmap' and 'telnet' but both failed.
The follow things I did to trying make this work:
iptables -I INPUT -p tcp --dport 25 -j ACCEPT
/sbin/service iptables save
/sbin/service iptables restart
OUTPUTS:
# iptables -L -n
Chain INPUT (policy DROP)
target prot opt source destination
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:32315
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8443
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:465
Chain FORWARD (policy DROP)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
# nmap localhost
Starting Nmap 5.51 ( http://nmap.org ) at 2014-02-08 01:46 CET
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000015s latency).
Not shown: 996 closed ports
PORT STATE SERVICE
80/tcp open http
443/tcp open https
2222/tcp open EtherNet/IP-1
8443/tcp open https-alt
Nmap done: 1 IP address (1 host up) scanned in 0.16 seconds
Best Answer
The iptables rule is fine, but according to nmap's output I don't think that you have any service running in that port.
Confirm that by running the following command:
If the output does not show anything in that port, be sure to start the appropriate service.