Westermo RedFox Series - Manual (Page 521)

Westermo OS Management Guide
Version 4.17.0-0
relay agent can be configured to forcibly override Option 54, the Server Identity
field. In effect, making sure that the client will send all DHCP messages via the
relay agent, see
fig. 23.3 .
DHCP Discover
DHCP Offer
DHCP Request
DHCP Ack
DHCP
Client
DHCP
Relay
DHCP
Server
time
DHCP Discover
DHCP Offer
DHCP Request
DHCP Ack
DHCP Renew Request DHCP Renew Request
DHCP Ack
DHCP Ack
Figure 23.3: DHCP Proxy Mode, all messages goes via the relay agent.
Hence, there are two levels of DHCP Proxy Mode support in WeOS.
❼ Hint to server: The WeOS relay agent adds sub-option 11 to option 82 in
all DHCP messages forwarded to the server, to hint the server to fill in the
IP address of the relay agent in the DHCP server identity field in the server
responses. If the server supports RFC5107[
18 ], the relay agent will act as a
server proxy towards the client ( fig. 23.3 ).
Note
The WeOS DHCP server ( chapter 22 ) supports RFC5107[ 18 ].
❼ Force identity override: The WeOS relay agent can force server identity
override by updating the packets sent towards the DHCP client. This fea-
ture can be useful in situations where the DHCP server does not support
RFC5107[
18 ]. Forcing DHCP server identity override is disabled by default.
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