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New Member

spanning-tree portfast trunk

Hi all,

i read that portfast should only be enabled on access ports  not on trunk ports.

when this command is used

spanning-tree portfast trunk?

under what cases we will use portfast command on trunk port ?

thanks

mahesh

  • LAN Switching and Routing
2 ACCEPTED SOLUTIONS

Accepted Solutions

Re: spanning-tree portfast trunk

Hi all,

i read that portfast should only be enabled on access ports  not on trunk ports.

when this command is used

spanning-tree portfast trunk?

under what cases we will use portfast command on trunk port ?

thanks

mahesh

Hi Mahesh,

You can use PortFast to connect a single end station or a switch port to a switch port. If you enable PortFast on a port that is connected to another Layer 2 device, such as a switch, you might create network loops. But you can enable portfast with router on stick case.where you have switch with trunk configured with router interface.

Hope to Help !!

Remember to rate the helpful post

Ganesh.H

Hall of Fame Super Blue

Re: spanning-tree portfast trunk

Mahesh

You are right in what you say ie. you shouldn't use portfast on a trunk link between switches. Where i have seen the portfast trunk command used is when you have a server that supports 802.1q trunking and is running multiple vlans on it's NIC.

Jon

16 REPLIES

Re: spanning-tree portfast trunk

Hi all,

i read that portfast should only be enabled on access ports  not on trunk ports.

when this command is used

spanning-tree portfast trunk?

under what cases we will use portfast command on trunk port ?

thanks

mahesh

Hi Mahesh,

You can use PortFast to connect a single end station or a switch port to a switch port. If you enable PortFast on a port that is connected to another Layer 2 device, such as a switch, you might create network loops. But you can enable portfast with router on stick case.where you have switch with trunk configured with router interface.

Hope to Help !!

Remember to rate the helpful post

Ganesh.H

New Member

Re: spanning-tree portfast trunk

Hi Ganesh,

Many thanks for good reply

New Member

spanning-tree portfast trunk

Hello Ganesh,

                        when i gone for interview ; they asked me suppose you have one L2 switch. you need to configure trunk port. when you configured trunk port ; before saving the running config you type portfast command ; what will the output ?...

waiitng for your reply.

Thanks & Regards,

Devendra

Hall of Fame Super Gold

spanning-tree portfast trunk

Devendra,

That's a trick question.  I will never, under any circumstances, configure my uplink trunk port with STP portfast. 

New Member

spanning-tree portfast trunk

Hello,

             i will be waiting for your answer.

Thanks & Regards,

Devendra

Hall of Fame Super Blue

Re: spanning-tree portfast trunk

Mahesh

You are right in what you say ie. you shouldn't use portfast on a trunk link between switches. Where i have seen the portfast trunk command used is when you have a server that supports 802.1q trunking and is running multiple vlans on it's NIC.

Jon

New Member

Re: spanning-tree portfast trunk

Hi jon.

thanks for great reply again.

just to be courious which servers are these which support 802.1q trunking.

thanks

mahesh

Hall of Fame Super Blue

Re: spanning-tree portfast trunk

mahesh18 wrote:

Hi jon.

thanks for great reply again.

just to be courious which servers are these which support 802.1q trunking.

thanks

mahesh

Mahesh

Nowadays it is VMWare servers where you see them participating in multiple vlans but before VMWare it could be any server that you wanted to be in more than one vlan and as long as the NIC supported it you could set it up that way.

Jon

New Member

Re: spanning-tree portfast trunk

You should almost never apply a spanning-tree portfast trunk command to another cisco switch.  If you go back to the basics... spanning-tree portfast allows the ports to skip the blocking to fowarding states and go immediately to forwarding.  The spanning-tree portfast trunk does the same but for trunk connections.  It is recommended to do this on vmware/ESX servers that require a multi-vlan use port, BigIPs, Netscreens, any non PAGP using device.

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