BroadCast Storm/Spanning Tree Lab

Overdash

Hello,

I have 7 Catalyst 3560-POE-48, a 3560G, a 3560 V2, and 2 3560-POE-24 switches. I have 8 switches with out of the box Spanning-Tree enabled that are connected together redundantly so that spanning tree can block off some of the ports.

I disabled Spanning-Tree on 2 switches that were connected into each other redundantly and plugged my laptop into one of them. BAM! Created my first Broadcast storm. Delighted, I wanted to see if my Spanning-Tree switches would automatically disable ports that are plugged into a switch having a broadcast storm, so I plugged in 2 links to my root bridge and 2 more links to the switches in the Spanning-Tree stack from my None Spanning-Tree switches.

The entire rack lit up like a Christmas Tree...
I do not understand why the Spanning-Tree enabled switches fell victim to the Non-Spanning-Tree Switches storm.

Does Spanning-Tree only prevent Broadcast Storms from forming but can't stop one that already exists from taking down the Spanning-Tree enabled network?

Thanks,

Overdash

Well,
thanks anyway guys but I think this happens because I don't have BPDU Guard enabled on my portfast interfaces.

Forsaken_GA

Overdash wrote: »

Hello,

I have 7 Catalyst 3560-POE-48, a 3560G, a 3560 V2, and 2 3560-POE-24 switches. I have 8 switches with out of the box Spanning-Tree enabled that are connected together redundantly so that spanning tree can block off some of the ports.

I disabled Spanning-Tree on 2 switches that were connected into each other redundantly and plugged my laptop into one of them. BAM! Created my first Broadcast storm. Delighted, I wanted to see if my Spanning-Tree switches would automatically disable ports that are plugged into a switch having a broadcast storm, so I plugged in 2 links to my root bridge and 2 more links to the switches in the Spanning-Tree stack from my None Spanning-Tree switches.

The entire rack lit up like a Christmas Tree...
I do not understand why the Spanning-Tree enabled switches fell victim to the Non-Spanning-Tree Switches storm.

Does Spanning-Tree only prevent Broadcast Storms from forming but can't stop one that already exists from taking down the Spanning-Tree enabled network?

Thanks,

Once you have a loop, you have a loop. What you need to do to prevent that sort of thing is enable storm control to rate limit traffic that results because of this once a loop is formed.

jahsoul

I'm just drooling over the equipment....lol.

*going back to eBay to look for 1 3560*

Overdash

jahsoul wrote: »

I'm just drooling over the equipment....lol.

*going back to eBay to look for 1 3560*

Ya, I get stoked about it as well. It's pretty crazy the way I get equipment. I got tons of old servers, switches, routers and so on from hardware deployments. They can't find anyone to buy the old stuff (and I'm definitely not throwing out suggestions) so they just give it to me. That's not even all the 3560's I have. My favorites are the 3560 V2's because they are quieter.