spanning-tree portfast trunk to HP virtual connect

Answered Question
Sep 29th, 2008
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We are implimenting etherchannles from the HP virtual connect to our swithces.


HP's suggested config is the following




Interface port-channel 1

swithport trunk encapsulaiton dot1q

switchport trunk allowed vlan 3,4,5

switchport mode trunk

spanning-tree port-fast trunk

!


interface gig0/1

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 3,4,5

switchport mode trunk

spanning-tree portfast trunk

!



Does spanning-tree portfast trunk seem correct?


What would be the benefit of this?

Correct Answer by Jon Marshall about 8 years 9 months ago

Certainly can. A lot of NIC's on servers these days are capable of running 802.1q.


Jon

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Jon Marshall Mon, 09/29/2008 - 10:01
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The benefit of this is that even though it is a trunk link it will still act as a portfast access port and not have to wait the full 50 seconds of listening/learning/forwarding.


The command is there specifically for end servers that are connected to the switch via a trunk link.


Jon

Mohamed Sobair Mon, 09/29/2008 - 10:08
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Hi,


OH ... Long time not see ,


Never set spanning-tree portfast on a trunk ports.. This could result in spanning tree loops , Portfast has to be set on access port where there are host connected not bridges.


HTH

Mohamed

Jon Marshall Mon, 09/29/2008 - 10:11
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Mohamed


Think that's the point. I agree it should never be set on uplinks to switches but it isn't in this case.


Jon

nygenxny123 Mon, 09/29/2008 - 10:46
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I guess I learned that things other than switches can perform "trunking"

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Jon Marshall Mon, 09/29/2008 - 10:53
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Certainly can. A lot of NIC's on servers these days are capable of running 802.1q.


Jon

louis-philippe.lison Thu, 11/04/2010 - 05:55
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Hi there!


Would you recommend to add "BPUDguard" along with porftast on the trunk in order to put the port in error-disabled state in case of BPDU received on the trunk?


Regards,


LLP

Bert Gevers Thu, 11/04/2010 - 06:52
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Basically,BPDU guard runs on ports which are configured with portfast and therefore, connect to end devices.


As these end devices never originate BPDUs, you should indeed configure BPDU guard to prevent spanning-tree loops

caused by miscabling/...


You can read up on BPDU guard at the following link:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a008009482f.shtml

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