Why we need multiple STG? 1

[sakult]

I am configuring a 8306 as a core switch and four of 5530 as access switches. Each 5530 will have its own VLAN, and all ports in all VLANs share the same STG (STG=1).

I wonder in what situation would someone need a multiple STG (says.. when do I need to to create STG2).

Thanks..

 

[jimbopalmer]

Any time STP has to reconfigure, there is some disruption of the network. If you use a link that is not dead reliable, I would use a different STG at each end so it does not involve both ends in re-discovery of the best tree.

I tried to remain child-like, all I acheived was childish.

 

[DaddyOfThree]

I'm sorry but I couldn't resist;

http://www.youtube.com/watch?v=O17OkbDyj24

Cheers!

 

[TDN2007]

i think when you are using switches from anther vendor rather than Nortel like Cisco for example.
but here in nortel you do not need STG because SMLT replace it works in some how.

Best regards.

 

[rrossird]

We Configure diferent STG when you need to connect, for example, this Nortel 8306 with diferents vendors (Cisco, Motorola, etc.)

 

[andy88]

Another use for multiple STG is;

Multiple STG are used for load balancing. for example if you had 2 core switches and an edge switch connected in a triangle one of the links to the edge would be blocking using only half the available bandwith.

with multiple STG you could put half of your vlans in one and the other half in another. Then by manipulating which switch is root bridge for each STG you can make a different link to the edge forward traffic and block. This gives you double the bandwidth as both links are used rather than just the one.

Cisco use per vlan spanning tree to do this.

 

[Yaoul]

Hi Sakult,

Aren't ERS5530 layer 3 devices ? Then, why would you have STP configured between those switches and the Passport devices ?
MSTP could be useful when the VLANs carried over your equipments include a high number of user ports. You could then configure several STGs in order to reduce the spreading of a STP re-calculation.
As soon as your OS versions enable you to configure BPDU Filtering, there's no more reason - in my own opinion - why you should think about implementing MSTP.
Regards,

Yaoul