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Spanning Tree config with Provision OS switchs

 
rodriguesrui
Occasional Contributor

Spanning Tree config with Provision OS switchs

Hi,

need some help to config this cenario with Spanning tree and Provision OS.

I had various vlans across the network. The core are 2x 2920 in a stack, and other switchs are 2530.

I think I have to configure the 2920 like root role, and block bpdus from links that have less speed but after some research I cannot get an example to do this from the beggining to end.

Can anybody help me with this?

config_switchs_pls.PNG

3 REPLIES 3
TerjeAFK
Respected Contributor

Re: Spanning Tree config with Provision OS switchs

I'm no STP expert, but here are a few thoughts.

If you want your 2920 switches to be STP root then you should start by going over STP priority in all your switches. Set the 2920 stack to priority 0 and check that your 2530 switches (and other switches in the same LAN) have lower priority (default is 32768).

You want the 2530 to use the 10G uplinks as long as they are operational, but switch over to 1G if the 10G links fail? This should happen autmatically without any configuration on the switches, since 10G interfaces have a lower root path cost than 1G interfaces. So the 1G uplinks should be blocked by STP in normal operation.

There is a 1G link between the two 2530 switches in your diagram. Is that by design? Normally you want traffic between edge switches to go through your core. Anyway, it would normally be blocked by STP since it would introduce a loop if active.

I'm not sure that the two switches on the right are, but if they require a 10G connection then you should concider connecting them to your core instead of edge switches.

rodriguesrui
Occasional Contributor

Re: Spanning Tree config with Provision OS switchs

Hi TerjeAFK,

thank you for your answer.

If you want your 2920 switches to be STP root then you should start by going over STP priority in all your switches. Set the 2920 stack to priority 0 and check that your 2530 switches (and other switches in the same LAN) have lower priority (default is 32768).

Well priority 0 for 2920 is the highest or the lowest? I think the command is: spanning tree priority 0 in 2920 stack, and it goes from 0 to 15.

You want the 2530 to use the 10G uplinks as long as they are operational, but switch over to 1G if the 10G links fail?

That is the idea.

This should happen autmatically without any configuration on the switches, since 10G interfaces have a lower root path cost than 1G interfaces. So the 1G uplinks should be blocked by STP in normal operation.

So, I do not have to configure manually path costs, to give priorioty to 10G uplinks over 1G uplinks?

There is a 1G link between the two 2530 switches in your diagram. Is that by design? Normally you want traffic between edge switches to go through your core. Anyway, it would normally be blocked by STP since it would introduce a loop if active.

In the 2530 in the middle, I will disable the copper uplink between the 2x 2530 in that rack. It really does not make much sense.

I'm not sure that the two switches on the right are, but if they require a 10G connection then you should concider connecting them to your core instead of edge switches.

The Switch on the right (3800) is connected with 2x 10G uplinks, and it was not physically possible to connect them to the Stack of the 2920, so this was the possible uplink connection.

The question is that the cost in the switch is the different for 10G or 1G uplinks. Example config of the command show spanning-tree in the 2920.

2/44 100/1000T | 20000 128 Forwarding | e0071b-5a6d0b 2 Yes Yes
2/A1 SFP+SR | 2000 128 Forwarding | e0071b-5a6d0b 2 Yes No

And in the 2530 in the middle, the uplinks are forwarding, for the same 2920 stack.

47 100/1000T | 20000 128 Forwarding | f0921c-8484c0 2 Yes Yes
48 100/1000T | Auto 128 Disabled | 2 Yes No
49 SFP+SR | 2000 128 Forwarding | e0071b-5a6d0b 2 Yes No

TerjeAFK
Respected Contributor

Re: Spanning Tree config with Provision OS switchs

STP priority 0 is the highest.

You should not have to configure path costs for each interface. 10G links will have 2000, while 1G links will have 20000. Lower path cost will be chosen.