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Spanning Tree setup

Jonathan Axford
Trusted Contributor

Spanning Tree setup

Hi Guys,

Here is a basic layout of my network. I am still not entirely sure how to set up the Spanning Tree config.
I have about 50 switches in total, Split into 7 VLANs. I have 2500,2600,2800,4100,5300 and 9300 series switches making up this network.

What is the best way to set up STP? I have read about multi spanning-tree, but not all of my switches will support this as far as i know.

I don't seem to suffer from any performance problems on the network, just like to know that i am doing everything right. I can supply any info, So if someone fancies taking a quick look, feel free!


Where there is a will there is a way...
Mohieddin Kharnoub
Honored Contributor

Re: Spanning Tree setup

Hi Jonathan

You have some points to talk about in your network ;

- The 9300s and 4100s doesn't support MSTP
- Sometimes the Spanning-Tree diameter is an issue because STP timers impose a maximum network diameter of seven.
- You have to select the Root switches for tyour network, especially if you have other redundancy protocols running like VRRP.

I think the basic setup is to have multiple STP instances based on how many Vlans you have, then decide which one of the 9300s will be the root and the backup root for each Vlan, and in this case you will have a redundant network with load balancing between the Vlans.

I just want to know if you are running VRRP on the 9300s ? and where ?

Anyway i can give you a brief idea about the design :

1- A16 and A40 will have 3 instances basically for Vlans 3, 6 and 200 , and say A16 is root for 2 instances and backup for the other, A40 backup for first 2 instance and root for the last.

2- The 9300 named Tech has no backup for its Vlan20 - 200, so if its down, both Vlans are down.

3- Vlan4 has no backup also on its core C/D.

4- Vlan16 has no backup on its core J5.

5- If you can somehow manage to connect Vlan20 AND 220 to another 9300 for backup to Tech, then you can run multiple STP instances, other wise just run Rapid RSTP on Tech.

6- Again if you can do the same on point 5 for Vlan4 and Vlan16.

We can do another way of redundancy for the networks on Vlan20, 220, 4, 16 but we need to know how is your design for at least on of these networks.

Good Luck !!!
Science for Everyone
Dmitry G. Spitsyn
Trusted Contributor

Re: Spanning Tree setup

A little correction !

93xx DO support MSTP beginning with the version 08.0.01c of the software.

Good luck,
Jonathan Axford
Trusted Contributor

Re: Spanning Tree setup

Hi guys,

Been a while updating this, so here is some more info.
All of our 9300 are configured as the default gateways for the VLANs. They have point to point links to the A40 and A16 switches and all particiapte in OSPF routing.

I have started to set up VRRP between A16 and A40, but the other 9300 switches are a single point of failure for there VLANS. They all have redundant routes back to A16 and A40, these 2 swicthes are used to connect our server rooms to the network.

I think the best option for Spanning tree, as suggested is to have a Seperate STP setup for each VLAN and in the case of A16 and A40, have a backup root bridge for the vlans.

I don't think there is anyway we can set up VRRP style redundancy for the 9300s that connect VLANs 4, 16 and 20. We could use one of the 5300's behind these switches as a backup for STP though, (I think???)

Anyway, going to start properly working on this now so any help much appreciated....

Where there is a will there is a way...