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Stackable NWay Ethernet Switch User's Guide
On the other hand, if the Aging Time is too short, many entries may
be aged out soon, resulting in a high percentage of received packets
whose source addresses cannot be found in the address table, in
which case the Switch will broadcast the packet to all ports, negating
many of the benefits of having a switch.
Filtering Database
A switch uses a filtering database to segment the network and
control communications between segments. It also filters packets
off the network for intrusion control (MAC Address filtering).
For port 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 defined by the user,
the switch will discard the packet.
Filtering includes:
1. 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.
2. MAC address filtering The manual entry of specific MAC
addresses to be filtered from the network.
3. Filtering done by the Spanning Tree Protocol Can filter
packets based on topology, making sure that signal loops don't
occur.
4. Filtering done for VLAN integrity. Packets from a
member of a VLAN (VLAN 2, for example) destined for a device
on another VLAN (VLAN 3) will be filtered.
34
Switch Management Concepts
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