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STP question

4. What is spanning tree (802.1D)? How it is related to switch configuration? What is Root Bridge, Designate Bridge, Back Bridge, BPDU (Bridge Protocol Data Units), port cost, maxage interval, hello interval in Span Tree Protocol (loop avoidance)?



Re: STP question

Spanning tree is a protocol to prevent frames from looping indefinitely in a redudant swithched environment.In this one among the participating switch is elected as root bridge and one switch in each LAN segment is elected as Designated bridge.Refer URL

Re: STP question

go through this link:

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Re: STP question

802.1D, among other newer variations, defines STP (spanningTreeProtocol); this is a 'loop avoidance' protocol to assure your network contains no loops.

Root Bridge -

responsible for providing BPDUs to Designated Ports.

Designated Bridge -

any bridge not the root bridge; these have 'designated ports' which tell the switch what port the Root Bridge can be reached from.

BPDU - bridge protocol data unit -

a data packet that is sent from the Root Bridge and propagated throughout the network to the designated ports of directly connected switches.

Port Cost -

a weight assinged to a link that STP can use to determine which is a better path to a destination.

MaxAge -

an STP timer parameter that can be set; determines the maximum time a switch will wait without receiving a 'hello' before it attempts an STP reconfiguration.

Hello -

an STP timer parameter that can be set; determines how often the Root Bridge generates BPDUs and sends them out; default is 2 seconds

Back Bridge -

never heard of the term. designated bridges may have a 'backup link' to the network that is in an STP blocked state, if that's what you mean.

please see the following link for much more STP info:

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