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New Member

which is best election to choose root bridge ? i have topology

hi ,

 

i  have a toplogy as below :

http://www13.0zz0.com/2014/08/17/12/125759738.png

im wondering which is the best choice to root bride ?

is it Core-1 switch at the top ??

 

or

 

distribution-2 switch in the middle of the network ??

 

note that core 1 is the highestperformance , and the distribution-2 switch lower performancr thatn core1 .

 

but here im asking 

which is better to elect the root bridge ?

 

 

regards

7 REPLIES
Cisco Employee

I dont see a topology

I dont see a topology attached, but, if your network is layer 2 all the way up to the core, then its better to have the core as the root bridge so that all the other devices could build a shortest path to the core.

New Member

hi , its layer 2plz look

hi , its layer 2

plz look here

http://www13.0zz0.com/2014/08/17/12/125759738.png

 

regards

New Member

could u see it now ? 

could u see it now ?

 

Cisco Employee

It was blocked by Websense.

It was blocked by Websense. alright.. i see this and for this topology, keeping core as the Root is the best option.

New Member

can you tell me why ??is it

can you tell me why ??

is it because better hardware ?

why not distribution-2 ???

i found below :

""Ideally the Root Bridge is as closest as possible to all access (edge) switches to minimize frame travel time"""

 

 

???????????????????

Cisco Employee

not because it has better

not because it has better performance. if you are running RSTP, every bridge is going to generate the BPDU. so, the performance doesnt matter.

 

if core is the root, every dist will have a ROOT port and ALT port to the core. so, even if 1 port fails, the other one will take over. even if both the links fail, they will converge towards the other dist leading to the core.

 

if dist-2 is the root, all of its links must be in FWD state.

 

if you think about upper left triangle,  link3-4, link 7 of dist-2 are designated FWD. link3-4 of core is Root FWD. link 7 of Dist-1 is Root FWD. so, which link would be blocked? the link 1-2. similarly, the link5-6 of dist-3 would be blocked. so, all the traffic from all the devices in the network will go through the dist-2. you wont be usign the link between dist-1, dist-3 to core at all.

New Member

Thank you

Thank you

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