Need assistance with STP Guard

SOLVED
SNSGS
Here to help

Need assistance with STP Guard

Not a network expert so need some assistance here.

I've two stacks in the same rack that need to be connected using Ethernet.

SNSGS_0-1622026707390.png

1. I'm planning to connect port 1 of the admin switches to port 2,3 & 4 of the core switch 1. Is this correct? If yes, then what should be the STP guard setting be on the core and admin switches for these ports.

2. If point 1 is incorrect, could you please advise which ports on admin switches be connected to the core switch and also the ST guard settings?

 

Thanks in advance.

 

1 ACCEPTED SOLUTION

Accepted Solutions
Bruce
Kind of a big deal

Re: Need assistance with STP Guard

I’m assuming your switches are properly stacked, one stack for the core, and one stack for the admin switches. If so, then you might want to look at link aggregation rather than using single links and relying on STP. Link aggregation bundles the links and means you can use the aggregate bandwidth of the links, rather than relying on STP which blocks all paths except for one.

 

I would take four ports on your admin switch stack, say ports 1 and 2 from switch one, then port 1 from switch two, and port 1 from switch three, and aggregate them all (under Switchports in the Dashboard select the four ports then click Aggregate, you should see an AGGR port appear at the end of the switch port list). On the core switches I’d aggregate ports 1 and 2 on both switches (same process to create another AGGR port). Then you put the four cables in between the two switches and the links should come up as a single logical 4Gbps link - no need for spanning tree.

 

The only Spanning-Tree change I’d recommend you still make is to ensure your core switch becomes the root bridge. Go to Switch -> Switch Settings, then under STP configuration, click the ‘Set the bridge priority for another switch or stack’ link, find your core stack and the set the priority low to make it the most likely root.

 

Hope this helps.

 

 

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6 REPLIES 6
Inderdeep
Kind of a big deal

Re: Need assistance with STP Guard

@SNSGS : check out the best practices 

https://community.meraki.com/t5/Switching/STP-guard-setup-best-practices/m-p/31165#M2628

Regards
Inderdeep Singh
www.thenetworkdna.com ( Awarded by Cisco IT Blogs award 2020)
Bruce
Kind of a big deal

Re: Need assistance with STP Guard

I’m assuming your switches are properly stacked, one stack for the core, and one stack for the admin switches. If so, then you might want to look at link aggregation rather than using single links and relying on STP. Link aggregation bundles the links and means you can use the aggregate bandwidth of the links, rather than relying on STP which blocks all paths except for one.

 

I would take four ports on your admin switch stack, say ports 1 and 2 from switch one, then port 1 from switch two, and port 1 from switch three, and aggregate them all (under Switchports in the Dashboard select the four ports then click Aggregate, you should see an AGGR port appear at the end of the switch port list). On the core switches I’d aggregate ports 1 and 2 on both switches (same process to create another AGGR port). Then you put the four cables in between the two switches and the links should come up as a single logical 4Gbps link - no need for spanning tree.

 

The only Spanning-Tree change I’d recommend you still make is to ensure your core switch becomes the root bridge. Go to Switch -> Switch Settings, then under STP configuration, click the ‘Set the bridge priority for another switch or stack’ link, find your core stack and the set the priority low to make it the most likely root.

 

Hope this helps.

 

 

View solution in original post

PhilipDAth
Kind of a big deal

Re: Need assistance with STP Guard

As @Bruce said, go for link aggregation.  Then it is loop-free (no spanning-tree issues).

https://documentation.meraki.com/General_Administration/Tools_and_Troubleshooting/Link_Aggregation_a... 

 

Also, configure one of the stacks as the root of the spanning tree.

https://documentation.meraki.com/MS/Port_and_VLAN_Configuration/Configuring_Spanning_Tree_on_Meraki_... 

SNSGS
Here to help

Re: Need assistance with STP Guard

@Bruce many thanks for the detailed response. I was able to successfully create the link aggregation between the stacks. Everything seems to be working well. I also lowered the priority of the core stack. Really appreciate your assistance.

SNSGS
Here to help

Re: Need assistance with STP Guard

Just a follow-up question based on the info you provided. 

Can I implement link aggregation for stacks that are connected by fibre? 

SNSGS_0-1622086555652.png

 

Bruce
Kind of a big deal

Re: Need assistance with STP Guard

@SNSGS, you sure can, so long as they are all the same (I.e all copper or all SFP-based). Exactly the same process, just select the appropriate ports. In your stack of 5 switches I’d still only use 4 links however just to keep it ‘sane’ on the core switch, and 4Gbps will probably be more than you need.

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