# IP address and port conflicts

All IP addresses and ports used for connections must be available for both receiving and sending data. Using the same IP address and port for two or more devices will cause a conflict between devices, and systems will fail to communicate with each other.

Do the following to check system network IP protocol:

1. Try to `ping` the relevant IP addresses, and check the HMI's DNS settings if required.

2. Run the `netstat` command. This command will display both incoming and outgoing network connections for a number of network interfaces.

If a repeat IP address is identified, contact the site system administrator for assistance.

If no duplicate IP address is found, contact the site system administrator to see if a firewall is blocking the access to the IP addresses and ports.