PowerConnect 6224 - Spanning Tree and Port Fast questions

1.  Can I have Port Fast enabled globally (with spanning-tree portfast default) even if I have other STP enabled switches connected to it?

Yes you can,Portfast configuration ignored when port is connected to another switch

Portfast Allows immediate transition to a forwarding state

Port still participates in STP

Used for non-switch devices

• Clients
• Servers
• Printers

Prevents unnecessary timeouts from DHCP servers

1.  If I do enable Port Fast globally do I need to also globally enable BPDU Filtering?  According to the Dell documentation:

1. If you enable BPDU filtering GLOBALLY and a port that has Port Fast enabled sends a BPDU, the switch will take that port OUT of Port Fast and allow it to make changes to the topology. 
2. If you enable BPDU filtering PER PORT and a port that has Port Fast enabled sends a BPDU, the switch will block that BPDU and keep the port in the forwarding state.

Does it make more sense to enable Port Fast globally and use BPDU Filtering to stop possible loops or should I enable Port Fast on a port by port basis?

What order do I do this in so as to not create a loop between my connected switches but also not lose the spanning tree functionality between them?  Globally enable Port Fast then globally enable BPDU Filtering?  Enable filtering and then enable Port Fast?

I combined these together, as I think they all will relate to each other. I would take a look at the Auto portfast command. Page 545:

http://support.dell.com/support/edocs/network/PC62xx/en/CLI/PDF/cli_en.pdf

The auto command will put a port into portfast mode if it does not see any BPDUs for 3 seconds. From my understanding you should not need to enable BPDU filtering. So with this you would enable the auto portfast  and leave STP enabled, I believe this will accomplish what you are trying to do, with little effort put forward.

BPDUs are exchanged regularly (every 2 seconds by default), because of this a port plugged to another switch should not hit that 3 second mark and it will not transition to portfast.

1. Is there anything special I need to know about connecting virtual switches?

In most cases you will use a General or Trunk mode between the switch and the virtual switch, instead of access mode. Here are a couple articles on the subject that may help.

http://www.dell.com/downloads/global/power/ps3q08-20080213-Ramos.pdf

http://www.vmware.com/files/pdf/virtual_networking_concepts.pdf

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1004074

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003806

Hope this information helps some. If there are any other questions, let me know and I will research it.

Thanks.

Thanks for the reply!

I looked into the auto-portfast command and tried it out but it didn't really seem to have the results I was looking for.  I ran it like this:

enable

config

interface range ethernet all

spanning-tree auto-portfast

But even ten minutes after none of the ports were reporting that portfast was enabled.  I tried it with ranges of ports as well but still portfast did not appear to be enabled.  

In the end I globally enabled portfast and also enabled the BPDU filter which should allow any ports with switches connected to automatically disable portfast.  So far so good.  We'll see what happens tomorrow I guess!

One thing I noticed after running the auto-portfast command was most of the ports starting showing their "Fast Link Operational Status" as true.  After checking the admin guide it sounds like Fast Link and PortFast are essentially the same thing.  When I globally enabled PortFast the Fast Link status returned to false so they must linked.

Maybe using the auto-portfast command actually places the port in Fast Link mode?

Thanks for keeping us updated. Sorry the Auto-portfast command did not work, I am really not sure why. Glad to hear you got things working though.