Dhcp Relay - Alcatel-Lucent 7705 Service Manual

DHCP Relay

The 7705 SAR provides DHCP/BOOTP Relay agent services for DHCP clients. DHCP is a
configuration protocol used to communicate network information and configuration
parameters from a DHCP server to a DHCP-aware client. DHCP is based on the BOOTP
protocol, with additional configuration options and the added capability of allocating
dynamic network addresses. DHCP-capable devices are also capable of handling BOOTP
messages.
A DHCP client is an IP-capable device (typically a computer or base station) that uses
DHCP to obtain configuration parameters such as a network address. A DHCP server is an
Internet host or router that returns configuration parameters to DHCP clients. A
DHCP/BOOTP Relay agent is a host or router (for example, the 7705 SAR) that passes
DHCP messages between clients and servers.
Home computers in a residential high-speed Internet application typically use the DHCP
protocol to have their IP address assigned by their Internet service provider.
The DHCP protocol requires the client to transmit a request packet with a destination
address of 255.255.255.255 (broadcast) that is processed by the DHCP server. Since IP
routers do not forward broadcast packets, the DHCP client and server must reside on the
same network segment. However, for various reasons, it is sometimes impractical to have
the server and client reside in the same IP network. When the 7705 SAR is acting as a DHCP
Relay agent, it processes these DHCP broadcast packets and relays them to a preconfigured
DHCP server. Therefore, DHCP clients and servers do not need to reside on the same
network segment.
The 7705 SAR supports up to 8 DHCP servers. DHCP Relay is supported on access IP
interfaces associated with VPRN and IES and on network IP interfaces.
DHCP Options
DHCP options are codes that the 7705 SAR inserts in packets being forwarded from a
DHCP client to a DHCP server. Some options have additional information stored in
suboptions.
The 7705 SAR supports the Relay Agent Information Option 82 as specified in RFC 3046.
The following suboptions are supported:
7705 SAR OS Services Guide
• circuit ID
• remote ID
• vendor-specific options
VPRN Services
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