spanning tree portfast default

oxzgan

Hello Guys,


At lab exams we have to configure these commands
spanning tree portfast default
spanning tree bpfuguard default


As per my understandings it enabled portfast on all ports including trunk.
Do we need to go to every trunk ports and disable portfast?
It s not said in workbooks.

rakem

oxzgan wrote: »

Hello Guys,


At lab exams we have to configure these commands
spanning tree portfast default
spanning tree bpfuguard default


As per my understandings it enabled portfast on all ports including trunk.
Do we need to go to every trunk ports and disable portfast?
It s not said in workbooks.

Switch(config)#spanning-tree portfast ?
  bpdufilter  Enable portfast bdpu filter on this switch
  bpduguard   Enable portfast bpdu guard on this switch
  default     Enable portfast by default on all [B]access[/B] ports

The command enables portfast on all access ports. So no you do not need to disable it on trunks.
Same for BPDU guard.... it wouldn't work to well on trunks

mikearama

This thread goes back a bit, but I have a similar question. I have a couple 3560's on my desk, and when playing around with task 1.23 in workbook 1, I made a mistake that I'm curious about.

I accidentally entered "Sw2(config)#default spanning-tree portfast default"... and oddly enough, it took. I didn't get the message about interfaces having portfast enabled and the possibility of loops, as you get when you enter the command properly.

I ran a "sh run | in spann", and there's no entry for something about portfast being globally allowed, where as, when I entered the command properly and ran the sh run, the expected spanning-tree command shows up.

I quick google found nothing directly quoting the command beginning with "default".

Any thoughts on the results of using the command as I have?
Mike

bermovick

I would assume it's because of the default you have prepending the command, making this a 'default' command, not a 'spanning-tree' command.

default                     Set a command to its defaults

So what you did was (I'd think) reset 'spanning-tree portfast default' to it's default settings (IE: off). I've only really ever used the default command on an interface so I can't be 100% sure, but it makes sense.

lsp2310

oxzgan wrote: »

Hello Guys,


At lab exams we have to configure these commands
spanning tree portfast default
spanning tree bpfuguard default


As per my understandings it enabled portfast on all ports including trunk.
Do we need to go to every trunk ports and disable portfast?
It s not said in workbooks.

Checked out the CCNP switching book and it states that "On switches of building access submodule, enable port fast globally so that there will be no need to go to individual port and enable the portfast. Remember to disable port fast on the uplink ports that connects to the distribution switches"

What I can suggest is to check it by yourself on your lab.

1. Check what are the trunk interface and its charactristic using 'show interface trunk' 'show interface (interface) switchport'
2. After you check the parameter of the ports, enable port fast gloabally and repeat the step 1, to check if it enables port-fast on the trunks.

BPDU guard comes hand in hand with port fast so the effect of enabling globally would have same effects. Please correct me if I am wrong here.

Please keep us posted.

reaper81

Portfast can be enabled globally or per port. If you enable it globally it is enabled on all access ports. It is not enabled on trunks unless you configured spanning-tree portfast trunk on the interface. Some people misunderstand this command. It is not supposed to be enabled on Inter Switch Links (ISL). It is supposed to go on ports that are trunking to end hosts like a VmWare server or such that has the need for multiple VLANs but will never send BPDU's.

Now here is a question to get you going. What is the difference between running bpdufilter globally or per port. To ge a gold star, are there any BPDU's sent out a port with BPDU filter enabled?

thadizzy

BPDU filter defined globally will act conditional so BPDUs will not get sent unless you receive BPDUs on the port, then you will start sending them too.
If you define it on the port you'll still not send out any even if you receive them on the port.


Sorry I see now that was not a question