Unable to Use Port 25 Within Linux

Products

• Data Loss Prevention Network Prevent for Email

Issue/Introduction

Symantec SMTP Prevent running on Linux fails to monitor port 25.

Resolution

All Linux ports below 1024 are restricted, which means programs cannot bind those ports without being the root account. This is expected Linux behavior. 

With Windows, you can work directly against port 25 without the restrictions. The recommended approach is to reroute port traffic and setup IP tables.

To reroute port traffic and setup IP tables:

1. From the Advanced Server Detection page, setup Prevent to use port 10025 by changing the attribute, RequestProcessor.ServerSocketPort, to a value of 10025.
   
2. Setup IP tables:
   
   iptables -N Vontu-INPUT
   iptables -A Vontu-INPUT -s 0/0 -p tcp --dport 25 -j ACCEPT
   iptables -I INPUT 1 -s 0/0 -p tcp -j Vontu-INPUT
   iptables -t nat -I PREROUTING 1 -s 0/0 -p tcp --dport 25 -j REDIRECT --to-ports 10025
   iptables-save > /etc/sysconfig/iptables 
   
   Note: Setting up the IP tables effectively reroutes the traffic from port 25 to port 10025.
   
   For more references on IP tables, see:
   http://www.frozentux.net/documents/iptables-tutorial/

https://help.ubuntu.com/community/IptablesHowTo

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