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TOPIC: Turning off spanning tree

Turning off spanning tree 10 years 11 months ago #12041

  • TheBishop
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Hi folks
I might have a requirement to completely disable spanning tree on a Cisco switch. What is the best way to achieve this? I know I can apply spanning-tree portfast to individual ports, but does this really turn spanning tree off?
Also there is an Etherchannel set up between this switch and its neighbour. Does the Etherchannel need spanning tree to work properly or does it have some other mechanism?
Thanks in advance
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Re: Turning off spanning tree 10 years 11 months ago #12052

  • jwj
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Portfast does not disable spanning tree, instead it modifies the process so that the port skips to forwarding. A way to ensure that a switch, hub, etc. is not plugged into a portfast switchport and cause problems is the use of bpdu guard. That way, if BPDUs are received on the port, it will be err-disabled. As far as etherchannels, they are considered one link to spanning tree, so yes, spanning tree runs over etherchannels too.

To turn off spanning tree, you have to do it on a per VLAN basis.
example:
switch(config)#no spanning-tree vlan 1
-Jeremy-
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Soanning tree 10 years 11 months ago #12081

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Thanks Jeremy
So I guess that means that an Etherchannel will still work correctly even if spanning tree is completely disabled?
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Re: Turning off spanning tree 10 years 11 months ago #12086

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I've never tried that before, so I wouldn't know for sure. The worst that could happen is one of the etherchannel ports could get blocked.
-Jeremy-
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Re: Turning off spanning tree 10 years 11 months ago #12099

  • Chris
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Bishop,

Ether-channel should still work without a problem when spanning tree is disabled. You just need to ensure you don't have any network loops to avoid running around trying to catch the 'looping' packets :)

By the way, why are you looking into disabling STP?
Chris Partsenidis.
Founder & Editor-in-Chief
www.Firewall.cx
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STP 10 years 11 months ago #12105

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It's a stupid idea really. We have a hardware encryption unit connected between a mini-LAN made up of two switches with an Etherchannel between them and our main LAN switch stack. We're seeing some problems with the encryptor which I think is software related but the supplier is trying to blame our hardware. One of their 'recommendations' is to disable spanning tree in case the port up/down during state changes is upsetting their unit. I can do it since I don't have any loops in the infrastructure but I don't think it will make a blind bit of difference
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