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Backbonefast & Uplinlkfast

Hello,

Ist advised to configure Backbonefast & Uplinlkfast at the same time on a 2950-T 24 . Design : 3 2950-T 24 connected in a Triangle.

Thanks

3 REPLIES
New Member

Re: Backbonefast & Uplinlkfast

You shouldn't need to implement backbonefast:

here are some details on uplinkfast:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094641.shtml

here are some details on backbonefast

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800c2548.shtml

Re: Backbonefast & Uplinlkfast

Hi,

if you are having only 3 switches in triangle in your network BackboneFast is not necessary.

Any link failure would be detected as a directly connected line failure.

UplinkFast would be enough.

BackboneFast is reasonable in more complex topologies where indirect line failure can cause problems.

For details see http://www.cisco.com/warp/public/473/18.pdf

Regards,

Milan

Gold

Re: Backbonefast & Uplinlkfast

As Steven and Milan have said, you don't need BackboneFast in your 3-switch triangle.

If your servers are connected to one switch, then make sure that switch is the Root Bridge in your Spanning Tree by running UplinkFast only on the other two switches. (If you run it on all three, there's no guarantee that the switch with the servers will be the Root Bridge.) This will give you a speedy recovery if you suffer a link failure on the forwarding link from the switch and the Root Bridge is working.

On any access port connecting to a PC, printer, server, or any kind of device that may be powered off and on frequently, run Spanning Tree PortFast. This will put the link into forwarding state sooner, and will prevent topology change notifications from being sent every time the link's status changes. NOTE: Do NOT run PortFast on the ports which connect the switches to each other.

If it's important to completely optimize your network, and you have only these 3 switches, you could reduce the STP Hello Time, Max Age, and Forward Delay parameters. Then, whenever the Root Bridge goes down, the election of a new Root Bridge would take half the time (14 to 24 seconds vs. 30 to 50 seconds). Don't change these parameters unless you understand exactly what you are doing, though; and keep in mind you will have to recalculate the values if you add switches later. Here's a link that explains it:

Understanding and Tuning Spanning Tree Protocol Timers

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094954.shtml

Hope this helps.

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