By default the DDP first NIC is configured as the following:
IP address: 172.16.5.4
Subnet mask: 255.255.0.0
The second NIC is generally dedicated for service connection and is configured so that it gets an IP address from DHCP.
Other NICs are configured with similar settings as the first NIC, with IP addresses like 172.18.5.4 for the 3rd NIC, 172.19.5.4 for the 4rd NIC, etc.
These settings can be modified by going to the DDP web GUI "network" page.
Before changing any settings in that page, please make sure that all clients using the port you want to edit disconnect from the DDP volumes.
You are free to modify all the settings mentioned above as long all network subnets do not conflict with each other, in other terms, each DDP port must be configured with a unique subnet which doesn't interfere with the other ones.
When trying to setup a port with settings which conflict with another port, the DDP will display an error message and won't apply the changes until you fix the conflict.
The same rule apply when configuring VLANs in your company as explained in the dedicated topic.