I have two servers running Linux. Server A is SAMBA domain controller and Server B is MAIL server(qmail)
My Server A has two NIC. One two my ISP(172.16.57.188/30) and the other to my LAN.(172.16.19.0/24)
Server A LAN IP = 172.16.19.230
Server A ISP IP = 172.16.57.190
Server B IP = 172.16.19.231
Server B also has a dial up option for backup if ISP is down
I have attached my iptable script.
If i set default INPUT Policy to DROP then incoming Mail stop coming.
I add a rule at the end of the script:
ipt -A -s 0/0 -d $LAN_IP -j REJECT
The above rule will also block nmap port scans.
I am not a pro in iptables. Just know scripting and adding intermediate level rules.Please let me know how to fix this