D-Link DGS-3204, Руководство пользователя

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Gigabit Ethernet Switch User’s Guide
Switch Management 27
♦
Bridge Forward Delay The Forward Delay can be
from 4 to 30 seconds. This is the time any port on the
Switch spends in the listening state while moving
from the blocking state to the forwarding state.
Observe the following formulas when you set the
above parameters:
1. Max. Age
=
2 x (Forward Delay - 1 second)
2. Max. Age
=
2 x (Hello Time + 1 second)
♦
Port Priority A Port Priority can be from 0 to 255.
The lower the number, the greater the probability the
port will be chosen as the Root Port.
Illustration of STA
A simple illustration of three Bridges (or the Switch)
connected in a loop is depicted in Figure 5-1. In this
example, you can anticipate some major network problems
if the STA assistance is not applied. For instance, if Bridge 1
broadcasts a packet to Bridge 2, Bridge 2 will broadcast it
to Bridge 3, and Bridge 3 will broadcast it to Bridge 1...and
so on. The broadcast packet will be passed indefinitely in a
loop, causing a serious network failure.
To alleviate network loop problems, STA can be applied as
shown in Figure 5-2. In this example, STA breaks the loop
by blocking the connection between Bridge 1 and 2. The
decision to block a particular connection is based on the
STA calculation of the most current Bridge and Port
settings. Now, if Bridge 1 broadcasts a packet to Bridge 3,
then Bridge 3 will broadcast it to Bridge 2 and
the
broadcast will end there.