Westermo RedFox Series - Manual (Page 519)

Westermo OS Management Guide
Version 4.17.0-0
add its relay information option to incoming DHCP requests, unless the request
already contains a relay agent information option (added by some ”downstream”
relay agent)
1 .
Below the possible policy settings are listed how the relay agent should handle
incoming DHCP requests already containing a relay agent information option. The
policy can both be specified globally (i.e., per relay agent), as well as on per port
basis.
❼ Discard: Drop requests already containing a relay agent information option.
❼ Forward: If the request already contains a relay agent information option,
keep that entry when forwarding the request towards your DHCP server(s).
❼ Replace: If the request already contains a relay agent information option, re-
place that with your own DHCP option 82 field when forwarding the request
towards your DHCP server(s).
❼ Append: If the request already contains a relay agent information option,
append your own relay agent information option field when forwarding the
request towards your DHCP server(s).
❼ Require: Discard requests lacking a relay agent information option. If the
request already contains a relay agent information option, keep that entry
when forwarding the request towards your DHCP server(s). This option may
be useful in topologies including a mix of relay agents supporting and not
supporting DHCP snooping (see
sections 23.1.4 , and 22.1.4.2 ).
When handling DHCP requests already containing a relay agent information op-
tion, the following mechanisms apply to all policies:
❼ Dropping requests lacking a giaddr: As of WeOS v4.17.0, incoming requests
containing a relay agent information option, but lacking a giaddr, will be
discarded.
❼ Keeping existing giaddr: When forward a request which already contains a
relay agent information option, the giaddr field will be unchanged.
As of WeOS v4.17.0 no validation is performed by the relay agent on relay agent
information option field(s) included in DHCP messages returned from the DHCP
Server. The relay agent information is always removed
2 before passing it back to
the DHCP client (PC), or to a relay agent closer to the PC. This behaviour may give
1 The exception is when policy ”Require” is configured - then the packet will be discarded if it
does not contain a relay agent information option.
2 If more than one relay information option is included, the last option is removed.
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