Debunk my spanning-tree config - 6509 Core Switch

Unanswered Question
Aug 28th, 2008

Some one else set this up, I'm trying to figure out why it was done this way. Seems a little excessive IMO.

There are currently 5 other switches connected with all vlans on them.

spanning-tree mode mst

spanning-tree portfast bpdufilter default

no spanning-tree optimize bpdu transmission

spanning-tree vlan 1,4-109,112-119,122-153,155-165,167-170,172 priority 16384

spanning-tree vlan 173-207,209-210,213-220,222,224-240,242-254 priority 16384

spanning-tree vlan 256-329,332-339,342-419,421-549,552-559,562 priority 16384

spanning-tree vlan 563-668,670-1000,2099-2100,2199-2200 priority 16384

spanning-tree vlan 2-3,111,121,154,166,208,211-212,221,223,241 priority 24576

spanning-tree vlan 255,331,341,420,551,561 priority 24576

spanning-tree vlan 110,120,171,330,340,550,560,669 priority 28672

!

spanning-tree mst configuration

name inf

revision 1

instance 1 vlan 110, 120, 171, 330, 340, 550, 560, 669

instance 2 vlan 2-3, 111, 121, 154, 166, 208, 211-212, 221, 223, 241, 255

instance 2 vlan 331, 341, 420, 551, 561

!

spanning-tree mst 0-1 priority 28672

spanning-tree mst 2 priority 24576

---Mike

I have this problem too.
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Francois Tallet Thu, 08/28/2008 - 13:31

Hi Mike,

As long as you are running in mst mode, all thee "spanning-tree vlan X priority Y" configuration lines are of no use for example. You can thus remove them and greatly reduce the size of your STP config.

It's hard to determine if they are really "excessive" though. They may be the legacy from a previous pvst config, and maybe the engineer who setup the MST config kept it in order to be able to fall back easily to pvst if necessary.

The "no spanning-tree optimize bpdu transmission" should not appear in the config. That's a bug. I'm amazed it's still showing up in recent releases. That's cosmetic anyway.

Regards,

Francois

jonesm111 Fri, 08/29/2008 - 07:08

Thanks Francois,

Are the three lines of no use since MST will carry all STP info for all vlan in the same BPDU's?

---Mike

Francois Tallet Fri, 08/29/2008 - 08:15

Hi Mike,

Careful, I'm not talking about the three lines in the MST configuration submode. I'm talking about the seven lines specifying priority for the different vlan instances.

In pvst mode, you run one instance per vlan. So you have all the stp parameters instantiated by vlan. That's why you can set in particular the priority on a per vlan basis.

In mst mode, you only have up to 65 different instances. The priority of the different instances are set using a similar CLI, but with the mst keyword instead of vlan (spanning-tree mst x priority y).

My point was just that in mst mode, the vlan configuration is ignored (and in pvst mode, the mst configuration is ignored). So if you run mst, you can clean up the vlan configuration.

But again, be careful that the "instance X vlan Y" configuration lines are part of the vlan to instance mapping of mst. They are definitely relevant for the mst mode;-)

Regards,

Francois

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