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STP Design Problem

Answered Question
Dec 17th, 2005
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Can I run different stp in the whole switched network? e.g. run pvst in access layer and rapid pvst in distribution layer


And do I need to turn on backbone fast and uplink fast feature in distribution layer switch if I run rstp in that switch?


Thanks for any help

Correct Answer by Georg Pauwen about 11 years 8 months ago

Hello Yong,


although RSTP is backwards compatible with (802.1D) STP, when you have a switch in the spanning tree topology that runs (802.1D) STP, all switches will revert to STP. So, in your situation, it would not be possible to run RSTP in the distribution layer, and STP in the access layer.

With regard to RSTP and Backbone/UplinkFast: both are natively used by RSTP, that is, RSTP as an enhancement to STP has incorporated both BackboneFast and UplinkFast into its normal operation. There is no need to turn these features on when you run RSTP, since RSTP is already using them anyway...

Does that make sense ?

Have a look at this document as well:


Understanding Rapid Spanning Tree Protocol (802.1w)


http://www.cisco.com/warp/public/473/146.html#topic1


HTH,


GP

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Correct Answer
Georg Pauwen Sun, 12/18/2005 - 01:22
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    2017 WAN

Hello Yong,


although RSTP is backwards compatible with (802.1D) STP, when you have a switch in the spanning tree topology that runs (802.1D) STP, all switches will revert to STP. So, in your situation, it would not be possible to run RSTP in the distribution layer, and STP in the access layer.

With regard to RSTP and Backbone/UplinkFast: both are natively used by RSTP, that is, RSTP as an enhancement to STP has incorporated both BackboneFast and UplinkFast into its normal operation. There is no need to turn these features on when you run RSTP, since RSTP is already using them anyway...

Does that make sense ?

Have a look at this document as well:


Understanding Rapid Spanning Tree Protocol (802.1w)


http://www.cisco.com/warp/public/473/146.html#topic1


HTH,


GP

Ted Haubein Mon, 12/26/2005 - 20:07
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RSTP-capable switches are fully interoperable with 802.1D switches. They simply fall back to 802.1D on a per-port basis when connected to older switches. 802.1D switches ignore 802.1w BPDUs because of their type value. Because of this interoperability, 802.1W capable switches require no special configuration -- 802.1W is active whenever 802.1D is.

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