Section 22.1.4 – Westermo RedFox Series User Manual
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Westermo OS Management Guide
Version 4.17.0-0
to avoid that the server receives packets directly from clients (in addition to
relayed packets).
Note
It is possible to configure the WeOS relay agent to forward DHCP mes-
sages to non-standard UDP ports on the server, see
❼ DHCP Server Source UDP port (client port): The DHCP server will send pack-
ets with source UDP port 68 by default. It is possible to set the source UDP
port to a non-default value.
❼ Enable/disable Duplicate Address Detection (ICMP Ping Check): Before a
DHCP server offers a client an address it will check that no-one is already
using that address. The server conducts this duplicate address detection
mechanism by attempting to ”ping” the IP address a couple of time to ver-
ify that it gets no response. Disabling ”ping check” can speed up address
assignment.
The ”ping check” mechanism is recommended for robustness and is en-
abled by default. Only consider disabling ”ping-check” if you are using static
leases.
Warning
The WeOS DHCP server does not store the lease table in persistent
storage. Disabling ”ping check” can therefore lead to situations where
a server reboot causes a host to be assigned an address, which was
already assigned to (and in use by) another host.
22.1.4
Running a DHCP server and relay agent on the same unit
There are situations when you wish to run a DHCP relay agent (
) on
the same WeOS unit as your DHCP server.
❼ IP per port on DHCP server unit:
describes how to use a
DHCP server and a relay agent to assign IP addresses per port on the DHCP
server unit itself.
❼ Non-”DHCP snooping” relay agents in switched topologies:
explains how to handle non-”DHCP snooping” relay agents in
switched (as opposed to routed) topologies. (An alternative approach is to
let the DHCP server listen to a non-default UDP port, see
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