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15426
December 10th, 2003 12:00
Ethernet loop and spanning tree question
We are using 3348's in several places. Last night we had someone create a loop by plugging a network cable into 2 network jacks. We do not currently have spanning tree enabled. I understand the concepts of it but am not familiar with the details. I do know that one needs to know what they are doing before deploying spanning tree across a medium size network. We also do not have broadcast control enabled on the switches where the loop was created.
I have 4 questions. Any suggestions would be greatly appreciated!
1. Would broadcast control have stopped this at the switch?
2. If I were to enable spanning tree am I correct that I would have to go and modify the setting (fast link) for every port? 99% of them are client ports.
3. If I used rapid spanning tree would I still need to turn on fast link?
4. Since I don't know enough about spanning tree yet to just roll it out is there any software that could have notified me of the loop so I could have gone to fix it?
Thanks!
Mike
Message Edited by mjrogers99 on 12-10-2003 08:43 AM
sentinel-master
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December 14th, 2003 20:00
Firstly do not be afraid of spanning tree - it is quitean easilly understood networking protocol. Just ensure that you choose one network switch as the LAyer 2 ROOT of the network and influene its ROOT PRIORITY by changing this parameter on the switch....ideally it should be the switch which is nearest or connected to a Layer 3 routing device (router)
1. Would broadcast control have stopped this at the switch?
No - you need to resolve the loop with spanning tree - otherwise packets will keep circulating forever and just clogg up your links
2. If I were to enable spanning tree am I correct that I would have to go and modify the setting (fast link) for every port? 99% of them are client ports.
You should still be able to use fastlink on client/server ports - as it just takes the port to forwarding mode in spanning tree.
3. If I used rapid spanning tree would I still need to turn on fast link?
Not sure if RSTP & Fast link are mutually exclusive on the 3348 - dell to advise
4. Since I don't know enough about spanning tree yet to just roll it out is there any software that could have notified me of the loop so I could have gone to fix it?
NOpe - thats why spanning tree was invented 20+ years ago, when Layer 2 bridges were first put together to make networks......and ensure a loop free topology.
mjrogers99
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December 15th, 2003 04:00
Andrew_Hicks1
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169 Posts
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December 15th, 2003 12:00
To answer Sentinal-Master's advice on RSTP and FastLink, it's still an option. The name, however, differs depending on the interface.
If you go through the web console, it's still called FastLink, and the setting can be found under Switch > Spanning Tree > Port Settings (I usually recommend clicking 'Show All', and then just selecting FastLink for all applicable ports).
If you're doing it from the CLI, go to configure an interface (you can also specify a range of interfaces on the 3324/3348 switches), and issue the command 'spanning-tree portfast' to enable the feature on the selected port(s).