Virtual Lan Environments - Novell NETWARE 6-DOCUMENTATION Manual

Virtual LAN Environments

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Novell DNS/DHCP Management Utility Administration Guide
When a client starts up, it sends a UDP broadcast message, called a Discover
packet, to address 0xFFFFFFFF over port 67 requesting an address.
The forwarder has an IP address on the network and acts like a DHCP server,
listening for Discover packets from clients on its LAN that are meant for a
DHCP server. The forwarder must be configured with the destination address
of the actual DHCP server on a different LAN segment that will provide
DHCP service.
The DHCP server must be configured to serve the subnet on which the
forwarder is located. The DHCP server must have a subnet address range to
provide service.
After receiving a Discover packet from a client, the forwarder reformats the
packet and sends it to the DHCP server. The DHCP server responds to the
forwarder with an Offer packet containing an address for the client.
When the forwarder receives the Offer packet from the DHCP server, the
forwarder contacts the client and provides the IP address and lease
information.
NOTE:
The BOOTP protocol, unlike DHCP, does not provide a mechanism for a
client to accept only a single offer of an IP address; therefore, the DNS/DHCP
Management Utility allows only the server that is specified as the default server in
a Subnet object to be assigned to any address ranges that include BOOTP
addresses. If you want to assign other servers to the address ranges, you should
change the address range type so that it doesn't include BOOTP. If the range type
includes BOOTP, you will not be allowed to change the DHCP server assigned to
the range.
In environments using a virtaul LAN (VLAN), multiple subnets might be
defined on one physical subnet. For example, one physical subnet might
contain several Class C addresses to form a larger address range than allowed
for a Class C address. To accommodate a VLAN environment, a Subnet Pool
object must be configured on the DHCP server to bind the multiple subnets
together.
If a forwarder forwards client requests from a physical subnet with multiple
subnet bindings and these subnets are bound to a single subnet pool, the
collection of addresses available in configured subnet address ranges are
available to all clients (DHCP or BOOTP) on that physical subnet. This is the
primary use of the subnet pool.