Operation Manual

Operations Manual

Bridging

Your switch operates as a transparent bridge to the Ethernet ports. As such,

it learns the source Media Access Control (MAC) addresses of all incoming

packets and ages out devices which have not been heard from for either a

user or the default-specified length of time.

The switch maintains a forwarding table with a maximum storage capacity of

2,048 MAC address (recall that 6 of these addresses are reserved by

developmental engineering). These Ethernet addresses are associated with

all of the devices that have been detected recently.

Your switch checks all incoming packets from each port for their destination

address against a Bridge Address Table. If a packet’s destination address is

not on the same network segment as the originating packet, the switch

forwards the packet to the network segment associated with that destination

address. However, if the packet’s source and destination address are on the

same network segment, known as local traffic, the packet is automatically

discarded (ignored) or filtered.

Bridge Address

Table

The switch creates and maintains a dynamic database of addresses which are

stored in a Bridge Address Table. Port information entries in the Bridge

Address Table are, in turn, used as a basis from which to compare and

examine every packet to determine its source address, segment origin and

port information.

If a packet’s MAC address is not already stored in the Bridge Address Table,

the switch adds the learned address, the associated port number and a timer

value that indicates the age of the dynamic Bridge Address Table entry.

Consequently, the switch knows the address and associated port number the

next time it sees that address. By using the information stored in the Bridge

Address Table, the switch is able to quickly forward each packet to the

correct port.

The switch learns addresses from all packets. When devices are added to the

network, removed from it, or relocated, you do not have to reconﬁgure your

switch. Your switch automatically learns all addresses.

An address stored in the Bridge Address Table is discarded if there is no

activity from that address after approximately five minutes. This aging

process ensures that the Bridge Address Table is not only continually

updated but only includes current entries.

Each entry which is automatically entered (a dynamic entry) includes:

❑ An Ethernet MAC address

❑ The port number of the LAN on which the address resides

❑ The age of the entry

Note that the procedure to assign a port number of the LAN for the above

address is also contained in the LAN Emulation menu (Port to ELAN

configuration screen).