Port Taking long to come up

[kamrannaseem]

Hi All,

I Just setup a cisco 3750 switch with 12.2(55)SE8 image, whenever I connect my laptop or another switch to it takes 20 minutes for the interface to go from orange to green.

any help will be much appriciated.

Many thanks.

[Karsten Iwen]

what's in the log at that time?

-- 
Don't stop after you've improved your network! Improve the world by lending money to the working poor:
http://www.kiva.org/invitedby/karsteni

[Seb Rupik]

Hi Kamran,

What 'spanning-tree' commands are you using on these switchports?

Ensure you have the following commnad enabled globally:

spanning-tree portfast bpduguard default

On all swithports connected to a Pc or server use:

spanning-tree portfast

When you are experiencing the problem, once the above commands have been used, use the following command to gain some insight as to whether it is a spanning-tree issue:

sh spanning-tree summary totals

cheers,

Seb.

[kamrannaseem]

Hi Seb,

Its the  light that stays orange for a while but the link comes up striaght away when i connect, I can ping it as well.

many thanks.

[Seb Rupik]

An amber light means the switchport is in a blocking state. Whilst this is happening, what is the output for:

sh int status err

[kamrannaseem]

Hi Seb

Thanks for your help, Issue is sorted with the help of the information you provide.

Just a quick one. what is the difference between these two commands.

spanning-tree portfast bpduguard default

spanning-tree portfast

Many thanks.

[Seb Rupik]

spanning-tree portfast ...is applied per-interface and is only active when the interface is in non-trunking mode. Essentially it means the port transitions into STP forwarding mode as soon as the link comes up. Without this a port would sit in a listening state for between 30-50 seconds.

spanning-tree portfast bpduguard default ...is enabled globally on the switch. When a switchport with port-fast enabled receives a BPDU it will put the interface in an errdisable state. You will then have to manually 'no shutdown' this interface to bring it back up. Obviously after you have investigated where the BPDU came from!

cheers,

Seb.

[kamrannaseem]

Hi Seb,

I have applied only spanning-tree portfast default globaly and it works fine but as soon as I apply

spanning-tree portfast bpduguard default it puts the ports connected to voice gateway to err-disabled but the ports connected to IP Telephony Servers are fine.

Here is my stp configuration on the switch:

spanning-tree mode pvst

spanning-tree portfast default

spanning-tree extend system-id

Sorry dont know much about STP

Many thanks.

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

For the gateway ports that error disable, and when using portfast and bpduguard global defaults, add to the interface:

spanning-tree portfast disable

spanning-tree bpduguard disable

NB: just disabling bpduguard will avoid the err-disable, but don't recommend having portfast active without bpduguard.

PS:

BTW, you might also consider using rapid-pvst, i.e. the global command:

spanning-tree mode rapid-pvst

[kamrannaseem]

Hi Joseph,

If I apply the following commands globally:

spanning-tree portfast bpduguard default

spanning-tree portfast default

and then on the interfaces where gatway is connected:

spanning-tree portfast disable

spanning-tree bpduguard disable

after applying these commands would it bring the interfaces straight away because i had issues with interfaces, they were taking 5 minutes to come up.

many thanks.

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

There may be a delay on the ports w/o portfast configured (i.e. the gateway ports); more so with regular STP (vs. rapid-STP).

PS:

I also wanted to mention, if you have not already done so, you might want to explicitly select your root bridge.  Usually the center of the L2 topology and/or where the gateway for the subnet resides.

[kamrannaseem]

Thanks Joseph,

I have got another switch configured with following global commands.

spanning-tree mode rapid-pvst

spanning-tree portfast default

spanning-tree portfast bpduguard default

no spanning-tree optimize bpdu transmission

spanning-tree extend system-id

and on in the interfaces I have only got.

spanning-tree portfast disable

Do you think this configuration is ok ?

This switch will be connected to two core switches via uplink and they have configured root bridge on one of the core switches.

Many thanks.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Do you think this configuration is ok ?

Yes, although you should only need to disable the global portfast and bpduguard settings on interfaces that connect to devices that err-disable the interface.  Also, ideally, you want all your STP, on all your devices, running rapid-PVST.