How to delete "spanning-tree instance ist path-cost xxxxx" line in switch configs (5412zl switch)

[quantum-it]

I have two 10GbE switchports on my HP 5412zl switch, configured in a trunk pair, and each is configured with spanning-tree admin-edge-port.  

However, each interface's individual configuration also contains the following config settings:

Example:
int A1
trunk trk1 trunk
spanning-tree instance ist path-cost 2000
spanning-tree admin-edge port

Other 10GbE interfaces on this same switch, are configure in trunk pairs, but DON'T have the 'spanning-tree instance...." entry in their config setttings.

Any ideas why this is happening, or what I can do to remove the "instance ist path-cost 2000" entry from each of their configurations?

Switch is running firmware version K.16.01.0004

[parnassus]

Isn't because (at some point) MSTP was enabled on your HP 5412zl switch? Are there multiple VLANs to justify the use of MSTP?

[qs-it]

Yes I have multiple vlanms on this switch, but none of the other switchports have a "spanning-tree instance ist path-cost xxxx" entry in their configs.   Only these two trunked switchports.

[16again]

If this command is also present on trk port, just remove it there with CLI
configure
interface trk_x  
no spanning-tree insta....

Did you setup the switches?  Or someone before you who has taken steps towards distributing traffic?

[qs-it]

This environment only has the single 5412zl switch at its core.   I set up the switch, and never recall a specific spanning-tree port cost entry for ANY switchport (my traffics needs are such that I don't need to be so specific with my spanning-tree costs), so I'm just trying to find out how to remove this specific entry for the TWO switchports on my backbone switch that have these entries.

I have a number of other switchport trunked together, in nearly the exact same configurations, that don't have this entry in their run configs.  The only switchport entry for their run configs in their vlan membership and the ports are set to admin-edge-port.

[Vince-Whirlwind]

I've seen these lines auto-added when I create trunks.

I always figured, "I should read the manual and find out why they auto-add these now", but I've never got around to it.

I wouldn't worry about port costs anyway.

The important thing is to have the correct spanning-tree priority on your "core" switch, and port costs won't matter.

[DhritimanDas]

To remove spanning-tree instance ist path-cost 20000 on interface 44, you will have to set the path-cost to auto. 

• Before configuring ‘spanning-tree instance ist path-cost 20000’ on interface 44: 

HP-2920-48G-POE+(config)# sh run int 44 

Running configuration: 

interface 44

   name "//LAN-to-MFN//"

   untagged vlan 1

   exit 

HP-2920-48G-POE+(config)# sh spanning-tree instance ist detail 

  Port                      : 44

  Enabled                   : Yes

  Role                      : Disabled

  State                     :

  Priority                  : 128

  Internal Path Cost        : Auto

  Internal Root Path Cost   : 0

  Regional Root ID          :

  Designated Bridge ID      :

  Designated Port ID        :

  Exceeded-hops BPDUs Count : 0

  TC Detected               : 0

  TC Flag Transmitted       : 0

  TC Flag Received          : 0 

• After configuring ‘spanning-tree instance ist path-cost 20000’ on interface 44:

HP-2920-48G-POE+(config)# spanning-tree instance ist 44 path-cost 20000

HP-2920-48G-POE+(config)# sh run int 44 

Running configuration: 

interface 44

   name "//LAN-to-MFN//"

   untagged vlan 1

   spanning-tree instance ist path-cost 20000

   exit

HP-2920-48G-POE+(config)# sh spanning-tree instance ist detail 

  Port                      : 44

  Enabled                   : Yes

  Role                      : Disabled

  State                     :

  Priority                  : 128

  Internal Path Cost        : 20000

  Internal Root Path Cost   : 0

  Regional Root ID          :

  Designated Bridge ID      :

  Designated Port ID        :

  Exceeded-hops BPDUs Count : 0

  TC Detected               : 0

  TC Flag Transmitted       : 0

  TC Flag Received          : 0

• To delete/remove spanning-tree instance ist path-cost to auto from 20000,please configure the following:

HP-2920-48G-POE+(config)# spanning-tree instance ist 44 path-cost auto

HP-2920-48G-POE+(config)# sh run int 44 

Running configuration: 

interface 44

   name "//LAN-to-MFN//"

   untagged vlan 1

   exit

HP-2920-48G-POE+(config)# sh spanning-tree instance ist detail

  Port                      : 44

  Enabled                   : Yes

  Role                      : Disabled

  State                     :

  Priority                  : 128

  Internal Path Cost        : Auto

  Internal Root Path Cost   : 0

  Regional Root ID          :

  Designated Bridge ID      :

  Designated Port ID        :

  Exceeded-hops BPDUs Count : 0

  TC Detected               : 0

  TC Flag Transmitted       : 0

  TC Flag Received          : 0

Hope this helps :)