The Branch Gateway supports the DHCP/BOOTP relay agent function. This is an application that accepts DHCP/BOOTP requests that are broadcast on one VLAN. The application sends them to a DHCP/BOOTP server. That server connects to another VLAN or a server that might be located across one or more routers that might otherwise not get the broadcast request. The relay agent handles the DHCP/BOOTP replies as well. The relay agent transmits the replies to the client directly or as broadcast, according to a flag in the reply message.
Note:
The same DHCP/BOOTP relay agent serves both the BOOTP and DHCP protocols.
When there is more than one IP interface on a VLAN, the Branch Gateway chooses the lowest IP address on this VLAN when relaying DHCP/BOOTP requests. The DHCP/BOOTP server then uses this address to decide the network from which to allocate the address. When there are multiple networks configured, the Branch Gateway performs a round-robin selection process.
When the DHCP/BOOTP server is configured to allocate addresses only from a single subnetwork among the different subnetworks defined on the VLAN, you might need to configure the Branch Gateway with the relay address on that subnet so the DHCP/BOOTP server can accept the request.
DHCP/BOOTP Relay in the Branch Gateway is configurable per VLAN and allows for two DHCP/BOOTP servers to be specified. In this case, the Branch Gateway duplicates each request, and sends it to both servers. This duplication provides redundancy and prevents the failure of a single server from blocking hosts from loading. You can enable or disable DHCP/BOOTP Relay in the Branch Gateway.
