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Multiple Instance Spanning Tree running configuration question

Moonark
Occasional Collector

Multiple Instance Spanning Tree running configuration question

I have a few Procurve 5412s running MST and firmware 15.08.0013.  From what I can tell, it appears to be configured correctly, however when I run the command "show run" against those devices and compare it to my 3500yls the output is a bit strange.  I have not set up multiple VLANs on the switch and am using VLAN 1 for everything until we finalize our new network designs.  I am using instance 1 for MST instead of the default of 0.

 

It seems that when I plug a cable into a port on the 5412s the similar lines appear in my running config to those below.  I do not see this behavior on my 3500yls.  These ports are not uplinks to any other switch, just edge ports.  I do have admin-edge-port set.

 

spanning-tree instance ist C8 path-cost 20000

spanning-tree instance ist L24 path-cost 200000

 

Is this normal behavior?

3 REPLIES
Packet-Ghost
Occasional Advisor

Re: Multiple Instance Spanning Tree running configuration question

Hi,

 

If you only have on vlan, there's not much point in using mstp, becuase the purpose of mstp is to use different path's for different vlans.

 

The path-costs are normal. These are the default path-costs based on the link-speed:

 

2 000=10gb

20 000= 1 gb

200 000= 100 mb

2 000 000=10mb

 

So if you do not configure it manually, the path-cost for a 1 gb link will be 20 000.

 

If you can explain why you want to use mstp and what it is you want to achieve it would be easier to help.

 

K.

Moonark
Occasional Collector

Re: Multiple Instance Spanning Tree running configuration question

I am in the process of adding multiple VLANs to the network and will be setting up the full redundancy with VRRP so it will be needed here very soon.  I know the port costs, but just wondering why they are showing up in my running config when I didn't set them.  Is this something because I just have 1 VLAN at the moment or something with the 5412s? 

Highlighted
Packet-Ghost
Occasional Advisor

Re: Multiple Instance Spanning Tree running configuration question

It's because you have enabled MSTP. All links have path-cost, it's just a matter of using the default values or if you override them manually.

 

A link will always have a link-cost and if you don't set it manually, it will use the default values:

 

http://en.wikipedia.org/wiki/Spanning_Tree_Protocol

 

K.