Allied Telesis AT-S21 - Manual (Page 39)

$70654#8VHU·V#*XLGH
3-7
6SDQQLQJ#7UHH#&RQILJXUDWLRQ
Menu: Bridging
Caution
The default Spanning Tree Protocol (STP) parameters are adequate
for most networks. Changing them without prior experience and
understanding of how STP works might have a negative effect on
your network.
The spanning tree algorithm prevents data loops when end stations
in extended networks send and receive packets through bridges.
The switch operates as a bridge to Ethernet ports. As a bridge, the
switch:
❑ Learns source MAC addresses of incoming packets by storing
the information in a forwarding table (see also MAC Address
Table in Chapter 4, page 4-11).
❑ Forwards the packet to the destination’s network segment if
the source is from a different network segment; or discards the
packet if the source and destination addresses are on the
same segment because all stations on the segment have
already received the packet.
❑ Ages out the addresses (deletes the information from the
table) if the address is undetected by any port within a user-
defined or a default elapsed time (300 seconds).
❑ Updates the MAC address table automatically as you add,
remove, or relocate devices on the network.
❑ Determines the quickest single route to a destination
according to switch ports or VLANs when you enable
Spanning Tree.
❑ Updates other bridges with topology information by
periodically sending bridge protocol data units (BPDUs).
Most users generally keep the default spanning tree parameters to
allow bridges to automatically reconfigure themselves if the
topology changes or if bridges become disabled.
If you want a brief overview of the Spanning Tree Protocol (STP)
before proceeding, go to Appendix A, Spanning Tree Concepts.