Qtech QSW-2870 Руководство пользователя онлайн [101/230] 481606

Qtech QSW-2870 Руководство пользователя онлайн [101/230] 481606
Chapter4 Router Configuration
3-7
this is not economical. DHCP Relay solves this problem. It provides relay service
between DHCP Client and DHCP Server in different network segment and sends
DHCP message to DHCP Server across network segment. So DHCP Client of
different network can use the same DHCP Server. And this saves cost and also
facilitate the centralized management.
DHCP Relay is between DHCP Client and DHCP Server of different network segment
and it provides relay service for DHCP Client and DHCP Server.
DHCP Server
Figure DHCP Application Environment Topology
Option82 Supported by DHCP Relay
When DHCP Server and DHCP Client are not in the same sub-network, if Client wants
to be allocated IP address from DHCP Server, DHCP Relay Agent must be used to
forward DHCP request packet. Before DHCP Relay Agent sends the DHCP message
of Client to DHCP Server, it can insert some option information so that the DHCP
Server can get Client information precisely and allocate IP address and other
parameters flexibly according to corresponding policy. This option is called to be
DHCP relay agent information option and option number is 82. So it also called to be
option 82 and related standard document is RFC3046.
Option 82 is the expanded application of DHCP option. Option82 is only a application
expansion, it will not influence the DHCP original application whether carrying
option82 or not. DHCP Server not supporting option82 receives the message inserted
option82 or DHCP Server supporting option82 receives message without option82,
these two cases do not influence the original basic DHCP service. If want to support
Client
Client
Internet
DHCP Relay
Client
Client

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