Unanswered Question
Apr 19th, 2007
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actually i have never used vlan 1 and interface vlan 1 L3 interface.

Recently i noticed a spanning-tree loop in my network. Although it worked before with no no spanning-tree vlan 1 disabled, now it caused the loop.Vlan1 was enabled automatically on switches, might be the loop appeared

after disabling spanning-tree for vlan1.

I believe that any vlan should be included to spanning-tree if you have redundant links between switches, even for VLAN 1

Correct me, if i am wrong.


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ankbhasi Thu, 04/19/2007 - 09:42
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Hi Leo,

Yes you are right if you have redundant links between switches and you are allowing some vlans on those redundant links then spanning tree should be enabled for those vlan.

Infact it is good practice to keep spanning tree enable always for all vlans and if you are planning to disable spanning tree for any vlans then a very detail and proper analysis should be done of all physical links in your lan before you make any decesion of disabling spanning tree for vlan.



*Pls rate all helpfull post

guruprasadr Thu, 04/19/2007 - 22:08
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HI Leo,

In Theory, VLAN1 is used only for Management. In Live networks Spanning-Tree will be disabled in VLAN1 & for VLAN1 assign as IP Address for Management of Switch in remote.

Donot assign any port to VLAN1 & another other features should be avoided for VLAN1.

Pls Rate if Helps.

Best Regards,

Guru Prasad R

Leo_Stobbe Tue, 04/24/2007 - 23:07
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I don't want to use VLAN1. I have already separate vlan for management purposes.

You are talking about the purposes of vlans.

But i asked for spanning-tree design in redundant configuration for vlan 1.

If you will disable spanning-tree for vlan 1 in redundant switch interconnection it should cause the loop.


ankbhasi Wed, 04/25/2007 - 00:23
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Hi Leo,

As I updated in my previous post if you have redundant link and you disable spanning tree for any vlan that is carried on that redundant link it will cause a loop.

So if you have redundant link and you want to disable spanning tree for vlan 1 or as a matter of fact for any vlan you also should remove that vlans from those redundant link. SO if your redundant links are trunk links then remove vlans 1 from those trunk links.

Again removal of vlan 1 from trunk is not allowed in old software releases and on some old platforms.




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