3Com CoreBuilder 3500, Руководство по внедрению, Страница: 134 / 592

134 C
HAPTER
7: B
RIDGE
-W
IDE AND
B
RIDGE
P
ORT
P
ARAMETERS
STP Bridge and Port
Parameters
On a bridge-wide basis, you can enable or disable the Spanning Tree
Protocol (STP) and set STP bridge parameters. On a bridge-port basis, you
can enable, disable, or remove STP and set STP bridge port parameters.
Administering
Bridge-wide STP
Parameters
You can set the following STP bridge-wide parameters:
■
STP state on a bridge — When STP is disabled on the system, the
bridge does not participate in the Spanning Tree algorithm and other
STP settings have no effect on bridge operation or network topology
calculations. If other devices on the network are running STP, then
these packets are bridged.
■
Bridge priority — The
bridge priority
influences the choice of the
root bridge and the designated bridge. The lower the bridge’s priority
number, the more likely it is that the bridge is chosen as the root
bridge or a designated bridge. The bridge priority value (
0x0-0xffff
)
is appended as the most significant portion of a bridge identifier (for
example:
8000 00803e003dc0
). It is a 2-octet value.
■
Bridge maximum age — The bridge maximum age determines
when the stored configuration message information is judged to be
too old and is discarded from the bridge’s memory. If the value is too
small, then STP may reconfigure the topology too often, causing
temporary loss of connectivity in the network. If the value is too large,
the network may take longer than necessary to adjust to a new STP
configuration after a topology change such as the restarting of a
bridge. A conservative value assumes a delay variance of 2 seconds
per hop. The recommended value is 20 seconds.
The value that you set for bridge maximum age is only used if the
system is selected as the root bridge. Otherwise, the system uses the
value that is assigned to it by the root bridge.
■
Bridge hello time —
Hello time
is the period between the
configuration messages that a root bridge generates. If the probability
of losing configuration messages is high, shorten the time to make the
protocol more robust. Alternatively, to lower the overhead of the
algorithm, lengthen the time. The recommended value is 2 seconds.
The value that you set for bridge hello time is only used if the system is
selected as the root bridge. Otherwise, the system uses the value that
is assigned to it by the root bridge.