# IP addresses for Layer 2 Engines

You can add IP addresses to system communication interfaces on Layer 2 Engines.

A Layer 2 Engine’s system communication interfaces (Normal interfaces) can have the following types of IP addresses:

- A Physical Interface can have one or more static or dynamic IP addresses. A Physical Interface can have multiple dynamic IP addresses only if you add VLAN Interfaces on the Physical Interface and the VLAN Interfaces have dynamic IP addresses. Otherwise, a Physical Interface can only have a single dynamic IP address.
- A VLAN Interface can have one or more static IP addresses or a single dynamic IP address.

You might need to define a contact address if you enter a private static address and NAT is used to translate it to a different external IP address. The external IP address must be configured as the contact address if other SMC components need to use the external IP address to contact the engine.