HIMA Himax X-COM 01, Manual, Page: 27 / 42

X-COM 01 4 Start-up
HI 801 011 E Rev. 5.00 Page 27 of 42
ARP Aging Time [s] A processor or COM module stores the MAC addresses of the
communication partners in a MAC/IP address assignment table
(ARP cache).
If in a period of 1x....2x
ARP Aging Time ...

... messages of the communication are received, the MAC
address remains stored in the ARP cache.

... no messages of the communication partner are received, the
MAC address is erased from the ARP cache.
The typical value for the
ARP Aging Time in a local network
ranges from 5...300 s.
The user cannot read the contents of the ARP cache.
Range of values: 1...3600 s
Default value: 60 s
Note:
If routers or gateways are used, the user must adjust (increase)
the
ARP Aging Time due to the additional time required for two-
way transmission.
If the ARP Aging Time is too low, the MAC address of the
communication partner is erased from the ARP cache, the
communication is delayed or interrupted
. For an efficient
performance, the ARP aging time value must be less than the
receive timeout set for the protocols in use.
MAC Learning MAC Learning and ARP Aging Time are used to set how quick the
Ethernet switch should learn the MAC address.
The following settings are possible:

This ensures that data packets cannot be intentionally or
unintentionally forwarded to external network subscribers (ARP
spoofing). Conservative (recommended):
If the ARP cache already contains MAC addresses of
communication partners, these are locked and cannot be
replaced by other MAC addresses for at least one
ARP Aging
Time and a maximum of two ARP Aging Time periods. This
encsures that data packets cannot be intentionally or
unintentionally forwarded to external network subscribers (ARP
spoofing).

Tolerant:
When a message is received, the IP address contained in the
message is compared to the data in the ARP cache and the
MAC address stored in the ARP cache is immediately
overwritten with the MAC address from the message.
The
tolerant setting must be used if the availability of
communication is more important than the authorized access to
the controller.
Default setting: Conservative
IP Forwarding Function is not supported, must be deactivated.
Default setting: Deactivated