User's Manual

User’s Manual of LRP-822CS/LRP-1622CS
145
highest Priority.
Hello T ello Time can be from This is the interval between two transmis ackets
sent by r S lo Ti itch, and it
is not th o Time d when your Switch becomes the Root Bridge.
Priority – A Priority for the switch can be set from 0 to 65535. 0 is equal to the
ime – The H 1 to 10 seconds. sions of BPDU p
the Root Bridge to tell all othe
e Root Bridge, the set Hell
witches that it is indeed the Root Bridge. If you set a Hel
will be used if an
me for your Sw
The Hello T a configuration error will ime cannot be longer than the Max. Age. Otherwise,
occur.
Max. Age – The Max Age can be from 6 s still not been received from
the Root Bridge, your Switch will start sen itches for permission to become the Root Bridge. If it
turns ou witch has the lowest
Forward Delay Timer – The Forward De econds. This is the time any port on the
Switch spends in the listening state while tate.
to 40 seconds. At the end of the Max Age, if a BPDU ha
ding its own BPDU to all other Sw
t that your S Bridge Identifier, it will become the Root Bridge.
lay can be from 4 to 30 s
moving from the blocking state to the forwarding s
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)
Port Priority – A Port Priority can be from 0 to 240. The lower the number, the greater the probability the port will be chosen as
Port Co t Cost c 0 to 200000000. The lower the num the probability the port will be
chosen kets
3. Illustration of STP
A simple il e bel ticipate
some major network problems
If switch A broadcasts a packet to switch B, switch B will broadcast it to switch C, and switch C will broadcast it to back to switch
e passed indefinitely in a loop, potentially causing a network failure. In this example,
STP breaks the loop by blocking the con ion between switc n to block a particular connection is based
on the STP calculation of the most ort settings.
Now, if switch A broadcasts a packet to switch C, then switch C will drop the packet at port 2 and the broadcast will end there.
Setting-up STP using values other than the defaults, can be complex. Therefore, you are advised to keep the default factory
settings and STP will automatically ass es/ports and bl p connections. Influencing STP to choose a particular
ority setting, or influencing STP to choose a particular port to block using the Port Priority
the Root Port.
st – A Por an be set from ber, the greater
to forward pac .
lustration of three switches connected in a loop is depicted in th
if the STP assistance is not applied.
ow diagram. In this example, you can an
A and so on. The broadcast packet will b
nect h B and C. The decisio
current Bridge and P
ign root bridg ock loo
switch as the root bridge using the Pri
and Port Cost settings is, however, relatively straight forward.