Solved: Re: 2960 not updating STP port cost according to bandwidth

netone.cisco · ‎07-22-2011

Hi all

We have a backhaul Cisco switched network with primary/backup links controlled by spanning-tree.

Today I noticed on one of the switches that changing the interface bandwidth is not updating the port cost on some of the ports. Any one had this happen before? I changed bandwidth, shut-noshut and nothing. Had to change cost with the "spanning-t cost" command.

This is only happening on some ports.

Please note that the cost below on fa0/24 is 21 because of the command. Before the command it was 21 even with "bandwidth 6000"

sa-ld-ccta-01#show span vlan 250

VLAN0250

Spanning tree enabled protocol ieee

Root ID Priority 24826

Address 0018.737e.f180

Cost 19

Port 23 (FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 33018 (priority 32768 sys-id-ext 250)

Address 0025.83d9.4380

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/3 Desg FWD 19 128.3 P2p

Fa0/23 Root FWD 19 128.23 P2p

Fa0/24 Altn BLK 21 128.24 P2p

interface FastEthernet0/3

description SEDE

switchport trunk allowed vlan 250,610,611

switchport mode trunk

bandwidth 32000

spanning-tree portfast

end

interface FastEthernet0/23

description UPLINK-TCC-FIBRA

switchport trunk allowed vlan 250

switchport mode trunk

bandwidth 46000

duplex full

storm-control broadcast level bps 1m 800k

storm-control multicast level bps 1m 800k

spanning-tree guard loop

end

interface FastEthernet0/24

description UPLINK-TCC-RADIO-BACKUP

switchport trunk allowed vlan 250

switchport mode trunk

bandwidth 6000

speed 100

duplex full

storm-control broadcast level bps 1m 800k

storm-control multicast level bps 1m 800k

spanning-tree guard loop

spanning-tree cost 21

end

Below the vlan610 summary on the same switch. as you can see some ports had the cost changed by the bandwidth command.

VLAN0610

Spanning tree enabled protocol ieee

Root ID Priority 25186

Address 0018.737e.f180

Cost 27

Port 22 (FastEthernet0/22)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 33378 (priority 32768 sys-id-ext 610)

Address 0025.83d9.4380

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/1 Desg FWD 19 128.1 P2p

Fa0/2 Desg FWD 100 128.2 P2p

Fa0/3 Desg FWD 19 128.3 P2p

Fa0/4 Desg FWD 125 128.4 P2p

Fa0/5 Desg FWD 19 128.5 P2p

Fa0/6 Desg FWD 166 128.6 P2p

Fa0/7 Desg FWD 166 128.7 P2p

Fa0/12 Desg FWD 19 128.12 P2p

Fa0/21 Altn BLK 21 128.21 P2p

Fa0/22 Root FWD 19 128.22 P2p

Cisco IOS Software, C2960 Software (C2960-LANBASE-M), Version 12.2(35)SE5, RELEASE SOFTWARE (fc1)

Please help.

Thanks

Peter Paluch · ‎07-23-2011

Hello,

Please read the original post more carefully - it already indicates what you have written:

Please note that the cost below on fa0/24 is 21 because of the command. Before the command it was 21 even with "bandwidth 6000"

To the original post: This behavior is quite confusing, and I do not remember seeing it on my switches. However, your IOS version (the 12.2(35)SE) is quite outdated. Do you have an option of upgrading to the most recent version, that is, 12.2(58)SE1? I suggest trying this version first. It may well be a bug - I do not see any obvious configuration error.

Please give it a try and let us know!

Best regards,

Peter

View solution in original post

Eduardo Aliaga · ‎07-22-2011

Notice you have the following command in your interface

interface FastEthernet0/24

spanning-tree cost 21

That's why the cost it's always 21, because you have defined it statically.

Peter Paluch · ‎07-23-2011

Hello,

Please read the original post more carefully - it already indicates what you have written:

Please note that the cost below on fa0/24 is 21 because of the command. Before the command it was 21 even with "bandwidth 6000"

To the original post: This behavior is quite confusing, and I do not remember seeing it on my switches. However, your IOS version (the 12.2(35)SE) is quite outdated. Do you have an option of upgrading to the most recent version, that is, 12.2(58)SE1? I suggest trying this version first. It may well be a bug - I do not see any obvious configuration error.

Please give it a try and let us know!

Best regards,

Peter

netone.cisco · ‎07-25-2011

Eduardo and Peter thanks very much for your time.

First of all correcting my original post, cost on fa0/24 was 19 (not 21) even with bandwidth 6000.

Peter,

I was considering this before but wanted to check the community experiences before. I will check the possibility of upgrade and schedule a window as this is a very important switch. I will let you all know how it goes

Regards

Mario Pinho

Peter Paluch · ‎07-25-2011

Hello Mario,

I understand, and you have approached this issue very correctly in my opinion. To me, it really appears like a bug, especially when considering the fact that on other ports of the same switch, the STP cost is computed correctly.

I am eagerly awaiting your news after you upgrade the IOS. Please note that the IOS 12.2(58)SE1 will upgrade your bootloader during its first bootup, and the switch will reload twice until the bootup is complete.

Best regards,

Peter

netone.cisco · ‎07-27-2011

Hi Peter,

Thanks for this. All will have the results by August 3rd. I believe I never had an upgrade that included a bootloader upgrade. From your text above I understand there will be no extra tasks from me for the bootloader upgrade.

Also, please tell me where you got this information? The only place I can think of is the release notes which i have with me

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_58_se/release/notes/OL24337.html and I cant find this note.

Peter Paluch · ‎07-27-2011

Hello Mario,

You are welcome. Yes, there are no special tasks for you, except making sure that the power supply is stable during the entire switch reload and double bootup.

Actually, I have this information based on my personal experience. I saw a new IOS performing a bootloader update at some point between releases 12.2(40)SE and 12.2(55)SE. Assuming that you are upgrading from an IOS version that is a couple of years old, it is safe to assume that your bootloader will be upgraded as well.

Best regards,

Peter

netone.cisco · ‎08-01-2011

Hi Peter and all reading.

Just finished upgrading to 12.2(58)SE1. Success!!

Before the upgrade:

VLAN0610

Spanning tree enabled protocol ieee

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/1 Desg FWD 19 128.1 P2p

Fa0/2 Desg FWD 100 128.2 P2p

Fa0/3 Desg FWD 19 128.3 P2p

Fa0/4 Desg FWD 125 128.4 P2p

Fa0/5 Desg FWD 19 128.5 P2p

Fa0/6 Desg FWD 166 128.6 P2p

Fa0/7 Desg FWD 166 128.7 P2p

Fa0/10 Desg FWD 19 128.10 Edge P2p

Fa0/12 Desg FWD 19 128.12 P2p

Fa0/21 Altn BLK 21 128.21 P2p

Fa0/22 Root FWD 19 128.22 P2p

After upgrade (and removing static stp costs)

VLAN0610

Spanning tree enabled protocol ieee

Root ID Priority 25186

Address 0018.737e.f180

Cost 42

Port 22 (FastEthernet0/22)

Hello Time 2 sec Max Age 20 sec For

Bridge ID Priority 33378 (priority 32768 sys-

Address 0025.83d9.4380

Hello Time 2 sec Max Age 20 sec For

Aging Time 300 sec

Interface Role Sts Cost Prio.Nbr Type

------------------- ---- --- --------- -------- ----

Fa0/1 Desg FWD 125 128.1 P2p

Fa0/2 Desg FWD 100 128.2 P2p

Fa0/3 Desg FWD 45 128.3 P2p

Fa0/4 Desg FWD 125 128.4 P2p

Fa0/5 Desg FWD 98 128.5 P2p

Fa0/6 Desg FWD 166 128.6 P2p

Fa0/7 Desg FWD 166 128.7 P2p

Fa0/12 Desg FWD 19 128.12 P2p

Fa0/21 Altn BLK 56 128.21 P2p

Fa0/22 Root FWD 34 128.22 P2p

Also, you were right about the boot rom upgrade.

Thanks very much

BR

Mario

Peter Paluch · ‎08-01-2011

Mario,

Thanks a lot for keeping us informed, and I am very glad to see that the upgrade did help indeed!

Best regards,

Peter