24-port NWay Ethernet Switch User’s Guide
Switch Management and Operating Concepts
49
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Max. Age
The Max. Age can be from 6 to 40 seconds.
At the end of the Max. Age, if a BPDU has still not
been received from the Root Bridge, your Switch will
start sending its own BPDU to all other Switches for
permission to become the Root Bridge. If it turns out
that your Switch has the lowest Bridge Identifier, it
will become the Root Bridge.
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Forward Delay Timer
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.
Note:
Observe the following formulas when setting the
above parameters:
Max. Age
=
2 x (Forward Delay - 1 second)
Max. Age
=
2 x (Hello Time + 1 second)
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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.
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Port Cost
A Port Cost can be set from 1 to 65535.
The lower the number, the greater the probability the
port will be chosen to forward packets.
Illustration of STP
A simple illustration of three Bridges (or three switches)
connected in a loop is depicted in
Figure 5-3
. In this example,
you can anticipate some major network problems if the STP
assistance is not applied. If Bridge A broadcasts a packet to
Bridge B, Bridge B will broadcast it to Bridge C, and Bridge C
will broadcast it to back to Bridge A ... and so on. The broadcast
