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203880
June 18th, 2012 13:00
PowerConnect 6224 - Spanning Tree and Port Fast questions
We recently added two PowerConnect 6224 switches to our environment. They are mostly used to connect end devices (Wyse clients, ESXi hosts, printers). They also have some small workstation switches and two NetGear 728's connected to them.
We had never touched the default spanning tree settings but now we are having issues with RSTP not putting ports in the forwarding state quick enough for our Wyse devices to get a DHCP address. The answer from Wyse is to enable Port Fast on our switches.
I've been reading up on RSTP and Port Fast and I have some questions.
- Can I have Port Fast enabled globally (with spanning-tree portfast default) even if I have other STP enabled switches connected to it?
- If I do enable Port Fast globally do I need to also globally enable BPDU Filtering? According to the Dell documentation:
- 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.
- 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?
- Is there anything special I need to know about connecting virtual switches?
nmuleski
20 Posts
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June 19th, 2012 17:00
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!
nmuleski
20 Posts
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June 20th, 2012 06:00
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?