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VH-2402-L3 Management Guide
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source MAC addresses and their associated port numbers,
are deleted from the table if they are not accessed within the
aging time.
The aging time can be from 10 to 1,000,000 seconds with a
default value of 300 seconds. A very long aging time can
result in dynamic forwarding table entries that are out-of-date
or no longer exist. This may cause incorrect packet
forwarding decisions by the switch.
If the Aging Time is too short however, many entries may be
aged out too soon. This will result in a high percentage of
received packets whose source addresses cannot be found
in the forwarding table, in which case the switch will
broadcast the packet to all ports, negating many of the
benefits of having a switch.
Static forwarding entries are not affected by the aging time.
Filtering
The switch uses a filtering database to segment the network
and control communication between segments. It can also
filter packets off the network for intrusion control. Static
filtering entries can be made by MAC Address or IP Address
filtering.
Each port on the switch is a unique collision domain and the
switch filters (discards) packets whose destination lies on the
same port as where it originated. This keeps local packets
from disrupting communications on other parts of the
network.
For intrusion control, whenever a switch encounters a packet
originating from or destined to a MAC address or an IP
Address entered into the filter table, the switch will discard
the packet.
Some filtering is done automatically by the switch:
•
Dynamic filtering – automatic learning and aging of
MAC addresses and their location on the network.
