Hello!
I would like to setup an NTP server for my Windows network using CentOS 6.3 with firewall turned on. As I learned the NTP protocol uses port 123 UDP. I have two NIC cards. One for internal network and one for access internet. Both cards in private address range. The problem is when I am using firewall described below the client cannot access the server. No idea why. Without firewall everything works flawless. So the problem is not in the NTP configuration. No idea why but with disabled firewall the first query gives error but all other query is work. I am using arpwatch to see what is happen on network (new machines and so). Not know is that related to the problem or not.
First I had used the system-config-firewall generated firewall (standard firewall with port 123:udp added). No success, client cannot connect.
Next I made a script for myself and saved with 'service iptables save' command. The configuration is:
eth0 10.0.0.99/24 eth1 10.0.1.10/24
The script for making firewall rules: iptables -P INPUT ACCEPT iptables -F iptables -A INPUT -i lo -j ACCEPT iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -p tcp --dport 22 -j ACCEPT iptables -A INPUT -i eth0 -s 10.0.0.0/24 -p udp --dport 123 -j ACCEPT iptables -A INPUT -i eth0 -s 10.0.0.0/24 -p tcp --dport 123 -j ACCEPT iptables -A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7 iptables -A INPUT -j DROP iptables -P FORWARD DROP iptables -P OUTPUT ACCEPT
Windows client time server is set to 10.0.0.99. Just for sure I enabled 123 TCP as well even I think that was unnecessary. The rule which related to NTP (123 UDP) increments its packet and byte count with 'iptables -L -n -v' so some connection was made. But no success on sync.
Any idea what is wrong?
Bye, a