DHCP

Gateway address Although the computers in the LAN can use ICMP redirects to learn which router is the correct virtual router, it is still advisable to designate the correct router as gateway directly during the DHCP negotiation. This allows the assigning gateway address to be determined as follows:

If a gateway is explicitly defined for the interface in the DHCP module, then only this will be assigned.
If no explicit gateway is set, then the default route is looked up in the routing table. If the default route exists and is connected to a virtual router which is directly linked to the interface through which the DHCP request is received, then the virtual router's address is assigned as gateway.
If other remote sites are linked to virtual routers, then these will not be assigned via DHCP since there can only be one default gateway. A host can only learn the corresponding routers via ICMP redirects.
Otherwise, the address corresponding to the address pool or interface (intranet or DMZ) will be assigned.

If more than one virtual router is connected by the default route, then the address of the router with the highest priority will be assigned. This allows for automatic load balancing through the selection of the DHCP server by the respective client. The DHCP server is to be activated on all routers involved in load balancing. All routers then define many virtual routers, each with different priorities. If the client randomly selects a DHCP server from those that answer, then it will also be randomly assigned a virtual router. Example with two routers Router A defines the following virtual routers:

Router ID	Virt. address	Prio	B-Prio	Peer
1	10.0.0.1	100	50	INTERNET
2	10.0.0.2	60	50	INTERNET

and, correspondingly router B:

Router ID	Virt. address	Prio	B-Prio	Peer
1	10.0.0.1	60	30	INTERNET
2	10.0.0.2	100	30	INTERNET

Depending on whether it chooses router A or router B, a DHCP client will now be assigned 10.0.0.1 or 10.0.0.2 as gateway and is initially distributed on both routers. Using this example, it becomes clear how load balancing can be combined with backup. If router A falls into backup mode, then router B will become the master for all clients. If router B fails, then router A will become the master for all clients and will attempt to establish its backup. If this fails, then it is LANCOM B's turn again (this signals the end of the backup chain).

Further addresses If the DHCP server is to assign explicit addresses for certain services which the device provides, such as a DNS server, then either the configured addresses or the real addresses are assigned to the respective interfaces. Assigning a virtual router violates the RFC, which prohibits a virtual router from offering other services. A device may only respond to a virtual address if it is the "owner" of this address, i.e. if this address is also the real address of the interface. At the same time, this means that DNS and NBNS must receive special treatment.