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Rajur

1 Rookie

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8 Posts

70

October 10th, 2024 08:23

STP mode change

Hello,

I need some advice. I found out one thing about our new customer that is probably generating some strange behavior. It has two data centers, each with two S5248F core switches in VLTs. These cores are then interconnected via dark fiber, which enables L2 stretch VLAN across both DCs.

And I found out that RSTP is running in one DC and Rapid-PVST in the other DC.

Is it possible to just switch RSTP to RapidPVST? Will there be "just" some potential unavailability up to 1min due recalculating topology? Or do I need to take some preparatory steps?

Thank you very much, R.

DELL-Chris H

Moderator

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9.5K Posts

October 10th, 2024 12:50

Rajur,

 

 

Yes, it is possible to switch RSTP to Rapid-PVST, but there are some considerations to keep in mind. Some of those would be;

  1. Interoperability : Since your current RSTP setup is already configured, you'll need to ensure that all devices in both data centers support Rapid-PVST. Check your switch firmware and configuration guides for compatibility.
  2. Configuration changes : You'll need to update your switch configurations to use Rapid-PVST. This may involve modifying VLAN assignments, spanning tree instances, and other settings.
  3. Network downtime : Switching protocols can cause network downtime, so plan for a maintenance window and ensure that you have a backup plan in place.
  4. L2 stretch VLAN : Since you mentioned L2 stretch VLANs, you'll need to verify that Rapid-PVST supports this configuration. Rapid-PVST is designed to handle multiple VLANs, but you may need to adjust the configuration to ensure seamless communication across the stretched VLANs.

So switching from RSTP to Rapid-PVST is possible, but it requires careful planning, configuration changes, and potential downtime. Before making the switch, ensure that all your devices support Rapid-PVST, and plan for network maintenance. I would also recommend you test the configuration changes in a lab environment before implementing them in production.

 

 

Let me know if this helps.

 

 

 

Rajur

1 Rookie

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8 Posts

October 16th, 2024 15:55

@DELL-Chris H ​ 

Hello Chris,

thank you for the answer and explanation!

I try to plan everything carefully. However, I have come across one thing that I am not sure about. From both DC sites, two DF lines are connected to a large office/HQ, where the network is built on Meraki, which only supports RSTP. How to configure it so that the Dell RPVST part works together properly with the Meraki RSTP? Should I set port type edge and delete "switchport access vlan 1" on Dell downlink ports to Meraki?

(currently, there is VLAN 1 everywhere, STP is blocking VLAN 1 it in this triangle between VLT)

Simplified scheme enclosed

Rajur

1 Rookie

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8 Posts

October 16th, 2024 16:07

unfortunately its failing to attach scheme, even via hotspot and in incognito tab mode.

But it is simple triangle:

VLT------DF-------VLT

      I                     I

       I                   I

      DF               DF

        I                 I

        I-Meraki--I

DELL-Chris H

Moderator

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9.5K Posts

October 16th, 2024 17:17

From the look of it, it might be easier for you to just switch it to rstp on the Dell switch rather than trying to make the cisco stuff use rpvst.

 

Dell Networking SmartFabric OS10 How to set up Virtual Link Trunking (VLT)

 

Now I'm not sure what the issue is with vlan 1, if it thinks there is a loop and is blocking it, you probably need to see if it is blocked on the Dell or Cisco switch side.

 

 

 

Rajur

1 Rookie

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8 Posts

October 18th, 2024 07:11

@DELL-Chris H ​ Hi Chriss,

finally, I switched all Dells to RPVST and filterout VLAN 1 from trunks between Dells and Meraki (RSTP). And it works, even for VLANs stretched through whole infrastructure...

Thanks for your consultancy

R.

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