Contemporary Control Systems Compact Managed Switches Software Manual for Web Browser - Manual (Page 30)

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4.4.5 Configure Filtering and Forwarding Table
An Ethernet switch learns which devices are tied to which ports by monitoring the traffic
carried through the switch. This information (MAC addresses and the ports to which
they are attached) is stored in the address table which holds up to 4000 address/port
associations. The switch will only transmit traffic destined for a registered address via
the specific port associated with that address. The table behaviour follows.
During frame reception, the frame’s destination address is compared with table entries
for a possible match. If a match is found, the port associated with the address is noted
from the table and the frame is directed to that port only. If no match is found, the frame
is flooded (transmitted) to all ports.
During the reception of a unicast frame, the frame’s source address is also compared
with table entries for a match. If a match is not found, the unregistered address (and
the port by which it arrived) will be added to the table. However, the address will NOT
be saved if the frame is from the Management Port or if the frame has an error or is
illegal in length — or if the table has no room for the new entry.
If a port-device association is not refreshed within the address table’s “MAC aging time”,
its information will be discarded. Figure 24 displays the typical MAC aging time of 300
seconds, but this can be set as high as 1048575 seconds (over 12 days).
Figure 24 — Configure Filtering and Forwarding Table
The screen of Figure 24 also provides options to display the two additional screens of
the Configure Filtering and Forwarding Table: Configure Multicast Filtering Table
(Section 4.2.5.5.1) and Configure Static Forwarding Table (Section 4.2.5.5.2).