FORE Systems ES-2810 Ethernet Switch User’s Manual
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Concepts in Switching
Concepts in Switching
A.8 Permanent Address Assignments
You can:
• See which ports have MAC addresses permanently attached to them
• Specify if other addresses are allowed to use individual ports
• Specify a permanent (locked) MAC address for each port
• Delete user addresses from the port list
A.8.1 Permanent Explanation
A.8.1.1 Address Table
The switch learns the topology of the network by matching the address of the station (which
sent the incoming frame) to the port on which it arrived. In this way it compiles an address
table of which stations are connected to each port.
Once an address is learned, a frame destined for that address is forwarded only on the port to
which it is attached. The switch removes “old” entries from the table to ensure that the
address table is always kept up-to-date.
A.8.1.2 Permanent Address
You can make stations permanent on a port so that they are never removed from the switch’s
address table regardless of how long they have been quiet.
Print servers are a good example of silent network devices — they are not able to send packets
to the switch and the MAC address is never learned by the switch.
A.8.1.3 Why Make Addresses Permanent?
If the switch receives a frame with an unknown destination address, it sends (or “floods”) the
frame out on all ports. You can reduce flooding by specifying permanent addresses on a port;
these addresses are not removed regardless of how long they have been quiet.
You can allow only the defined MAC address(es) for a port to be able to use that port, thus
increasing security by preventing the intrusion of unknown devices.
Unfortunately, defining permanent addresses on the ports can reduce your network’s ability
to move stations from one port location to another.
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