Ip Routing - Enterasys VH-2402-L3 Management Manual

For two DHCP servers to communicate across
different subnets, the BOOTP/DHCP Relay of the VH-
2402-L3 must be used. The DHCP servers are
identified by IP addresses.

IP Routing

IP handles the task of determining how packets will get from
their source to their destination. This process is referred to
as routing.
For IP to work, the local system must be attached to a
network. It is safe to assume that any system on this
network can send packets to any other system, but when
packets must cross other networks to reach a destination on
a remote network, these packets must be handled by
gateways (also called routers).
Gateways connect a network with one or more other
networks. Gateways can be a computer with two network
interfaces or a specialized device with multiple network
interfaces. The device is designed to forward packets from
one network to another.
IP routing is based on the network address of the destination
IP address. Each computer has a table of network
addresses. For each network address, a corresponding
gateway is listed. This is the gateway to use to
communicate with that network. The gateway does not have
to be directly connected to the remote network, it simply
needs to be the first place to go on the way to the remote
network.
Before a local computer sends a packet, it first determines
whether the destination address is on the local network. If it
is, the packet can be sent directly to the remote device. If it
is not, the local computer looks for the network address of
the destination and the corresponding gateway address.
The packet is then sent to the gateway leading to the remote
network. There is often only one gateway on a network.
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