STP Problems

[steff006]

Ok, so I've heard many different opinions about how to configure STP in the network. I want to know what is the correct way to configure STP between the distribution switches and the access switches? We have redundant links going between them.

Here is the current configuration for the distribution switch

spanning-tree mode rapid-pvst

spanning-tree loopguard default

no spanning-tree optimize bpdu transmission

spanning-tree extend system-id

spanning-tree uplinkfast

spanning-tree backbonefast

Also spanning tree is turned on for every vlan on the switch

EX: spanning-tree vlan ####

Here is the config for the access switch

spanning-tree mode pvst

spanning-tree portfast bpduguard default

spanning-tree extend system-id

spanning-tree uplinkfast

spanning-tree backbonefast

But we have spanning-tree turned off for the vlans on the switch

EX: no spanning-tree vlan ###

What is the correct way to have spanning tree configured on both switches and should we allow spanning tree for the vlans on the access switch?

[milan.kulik]

Hi,

it's difficult to tune STP without knowing basic info (how many switches are involved, which HW types, IOS, topology).

So just some general rules:

1) It's very DANGEROUS to turn off STP even on access switches. Any user can easily crash your network creating a loop connecting a hub to two switch ports, e.g.

2) "RSTP (IEEE 802.1w) natively includes most of Cisco's proprietary enhancements to the 802.1d spanning tree such as BackboneFast, UplinkFast, and PortFast." See http://www.cisco.com/warp/public/473/146.pdf for details. So it has no sense to configure these features when RPVST mode is enabled.

I don't know absolutely how loopguard (http://www.cisco.com/warp/customer/473/84.pdf) interacts with RSTP. I've got a feeling it's either ignored or increases the convergence time.

3) I'd be very careful running RPVST in the core/distribution layer and PSVT in the access layer. This could bring you some troubles. I'd recommend to run either RPVST or PVST in the whole network.

If you are a beginner I'd recommend PVST - it's stable, well documented and supported on all Cisco devices for a long time.

RPVST is faster, but new, more complex, no so well documented, not supported on all platforms and still containing some bugs. So it requires an advanced administrator, I think. (I didn't dare to run it in my productuion network yet, personally).

Regards,

Milan

[steff006]

We have 3500XLs and 3550s running the access layer switches. The 3500XLs are running Version 12.0(5)XU

and the 3550s are running Version 12.1(19)EA1c. We have approx. 75 closets that have redundant links going to them with about 3-5 switches in each closet. There are two core/distrubution closets that run these switches, with two 6513 in each closet.