Amer Networks SS3GR24i - Manual (Page 27)

SS3GR24i/SS3GR48i Layer3 Stackable Gigabit Switch User’s Guide
forwarding table entries that are out-of-date or no longer exist.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.
Filtering occurs to keep local traffic confined to its
segment.
• Filtering done by the Spanning Tree Protocol, which can
filter packets based on topology, making sure that signal
loops don’t occur.
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