Answered Question


I Have to know WHAT Is the function of these;in Lan Switching:





2)does spanning-tree backbone fast just on the CORE Switch?or on all switch inside networks

3)what is the function of the Spanning-Tree bpdu gard?does gard or filter is more efficient?


I have this problem too.
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Correct Answer by ankbhasi about 9 years 7 months ago

Hi Ali,

Alternate ports lead to the root bridge, but are not root ports. The alternate ports maintain the STP blocking state.



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Overall Rating: 5 (3 ratings)
ankbhasi Fri, 04/20/2007 - 11:21

Hi Ali,

I missed that from your original post.

DP means designated ports and RP means root port.

Read this link

Under Spanning Tree Algorithm it has explained it very nicely with Figure 23-3

Please come back if you have any dobts on the same.

By AP do you means Access Port? If yes access ports are normal ports on which you connect end hosts or end devices and which supports single vlan as compared to trunk ports which supports multiple vlans at a same time.



twarner28 Fri, 05/22/2009 - 22:53

DP is designated Port. For each network segment, there is elected one Designated Bridge. The Designated bridge is determine to have the lowest root path cost to the root bridge (which is upstream). This Designated Bridge will provide a DP for that segment. Basically everyone sends traffic towards the Designated Port to pass traffic up the STP.

RP is selected on per bridge. It's the one port sending traffic towards the root bridge.

AP is alternate port - think of it as the backup to the root port for a bridge. It's in blocking state. If RP fails, an AP will become RP.

Backbone fast is turned on on all switches.

BPDU Guard will put port into err-disable when it receives a BPDU. BPDU Filter will prevent sending of BPDU's.

Efficiency? That depends on your goal. BPDU Guard good if you want to shut down ports when switch is connected. BPDU filter can actually do into STP negoations if enabled globally, but will just ignore BPDU's if enabled locally.


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