IP addresses and inter-VDOM links
Besides being virtual interfaces, here is one main difference between inter-VDOM links and regular interfaces— default inter-VDOM links do not require IP addresses. IP addresses are not required by default because an inter-VDOM link is an internal connection that can be referred to by the interface name in firewall policies, and other system references. This introduces three possible situations with inter-VDOM links that are:
• unnumbered - an inter-VDOM link with no IP addresses for either end of the tunnel
• half numbered - an inter-VDOM link with one IP address for one end and none for the other end
• full numbered - an inter-VDOM link with two IP addresses, one for each end.
Not using an IP address in the configuration can speed up and simplify configuration for you Also you will not use up all the IP addresses in your subnets if you have many inter-VDOM links.
Half or full numbered interfaces are required if you are doing NAT, either SNAT or DNAT as you need an IP number on both ends to translate between.
You can use unnumbered interfaces in static routing, by naming the interface and using 0.0.0.0 for the gateway. Running traceroute will not show the interface in the list of hops. However you can see the interface when you are sniffing packets, which is useful for troubleshooting.