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Root Switch

having 6509 & 3750, running HSRP, i am not confident in making 1 as a root switch. does it affect the network immediately if i make 1 as a root switch? because i am worried if something goes wrong(being a live network running 24/7)

is the command OK if i put it in 3750 & 6509?



set spantree root 1,2,5,182-205




spanning-tree vlan 1,2,5,182-205 root primary

diameter option is also there, do i need to put that one also, if not which number should i put, if i doesn't put the diameter, what will happen?

do i need to put something else also? if so suggest me.


Re: Root Switch

Changing the Spanning Tree root bridge will change your topology. If you're running 802.1d, you would not want to do this during office hours.

The diameter and timers should not be changed unless you have a good reason for it. The current hello, max_age and fwd_delay are based on a diameter of 7 bridges.


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Re: Root Switch

how will i come to know whether it is running 802.1d? does it mean the trunking protocol 802.1q? & the command what i have specified is enuf?

Re: Root Switch

Hi Anand,

802.1d is one of the flavors of STP. Like RSTP is bsed on 802.1w standard and MSTP is based as 802.1s

Same way spanning-tree plus (PVST+) protocol based on the IEEE 802.1D standards.



Re: Root Switch


Changing the STP parameters will make STP to converge and there will be for sure effect in the network.Better to take downtime and do it.because if STP converges there might be some links going up/down.



Re: Root Switch

Hi Anand,

In addition to the other post you can configure only one root bridge for one vlan in your network. But as per your command you are trying to configure 3750 and 6509 root for same vlans.

You can keep 6509 root for few vlans and 3750 as secondary root for those vlans and same way for rest of the vlans you can configure 3750 as root and 6509 as secondary root and this will take care of redundancy and load sharing for spannning tree also.

And as others have suggested arrage a window as STP change for root will converge the whole network.

HTH, is yes please rate the post.


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