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automatic change of RSTP priority on core switch + track command

Hi All ,

We have setup where CS01 is connected to WR01 ( L3 interface ) and CS02 is connected to WR02 (L3 Interface).

Wr01 alink will be acting as active where as WR02 Link is standyby.

Configured RSTP on both core switches and Priority is also configured per vlan basis.

CS01 is root bridge and HSRP active for all vlans configured where as CS02 is HSRP standby.

We have used track command on all L3 vlan interfaces to track 2/20 port which is connected to WR01 .

Whenever 2/20 port of CS01 switch goes down , then HSRP will be active on CS02 and standby on CS01 switch.

is there any track command which can used under L2 vlan's so that whenever port 2/20 goes down , it automatically reduces RSTP priority to lower than RSTP priority configured on CS02 which makes CS02 as root bridge per all vlan's

.

My goal is whenever  " LAN uplink port between CS01 to WR01 goes down"  , CS02 should become Root bridge and HSRP should be active for all vlan's instead of CS01 switch.

CS01 has RSTP priority of 100 and HSRP prioroty of 200

CS02 has RSTP priority of 200 and HSRP prioroty as default.

OSPF is IGP between Core switches and CE routers.

Thanks ,
M S K       

Thanks , M S K
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5 REPLIES

automatic change of RSTP priority on core switch + track command

You should be able to do this with an eem script, but I'm not sure you're going to be able to do it via tracking. You can track the interface and then run an eem script to make the changes to stp for you. Let me know if you'd like to go this direction and I can help you with the script.

HTH,
John

*** Please rate all useful posts ***

HTH, John *** Please rate all useful posts ***
Hall of Fame Super Blue

Re: automatic change of RSTP priority on core switch + track com

Apologies John i seem to be invading all your posts

MSK - I'm not sure why you want to do this. If the HSRP router changes traffic will simply go from the access switch to CS01 across the interconnect to CS02 and then to WR02. So the only difference is traffic must go across the interconnect but there is nothing wrong with that and it shoud not even be noticeable in terms of any delay.

If you try and change the STP priority to be CS02 then STP will need to reconverge because now you have a new root bridge and that will cause a delay even with RSTP.

Is there a specific reason why you want to do this ?

Jon

automatic change of RSTP priority on core switch + track command

Jon,

No worries   I like seeing your answers!

HTH, John *** Please rate all useful posts ***
New Member

Re: automatic change of RSTP priority on core switch + track com

Hi Jon / John ,

Thank you for your valuable info.

There is no particular reason for doing this.just we want to eliminate CS01 whenever CS01 to WR01 LAN interface gets down so that all traffic would go through CS02 to WR02.

As you said , STP goes for reconverge once priority value changes on CS01 to select root bridge and remanining things.

Can we use any track command which reduces STP priority lower than CS02 switch under L2 vlan ..

Is it achieveble ?

I never run script for alerting STP priority .

Thanks ,
M S K

Thanks , M S K
Hall of Fame Super Blue

automatic change of RSTP priority on core switch + track command

As John said, i think you would need to use an EEM script for what you want to do.

You are probably going to lose some packets though each time you run the script as STP reconverges and i can't see why you would want to do that in a redundant network.

Jon

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