spanning-tree portfast trunk

[mahesh18]

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

[wuliting]

thanks for this information. 

I also configure this firewall to switch trunk port with spanning tree portfast trunk.However, sometime i encounter the error disable (sometimes) on that switchport. i manually shutdown and no shut again.

any expert have any advice for this? 

thank you

[andrespne]

hello,

I have an Access Point on bridge mode passing several Vlans connected to a 4500 on a trunk port.

Should i enable spanning-tree portfast trunk?

Also whats the difference between "spanning-tree portfast" vs "spanning-tree portfast trunk" ?

Thanks

Andres

[bradharrell5642]

I'm actually in the same situation with an access point on a trunk link, and have the same question.Im seeing constant flapping on the link that does not have port fast enabled. I checked and all other access points have this enabled on the port

[Silviu Pietris]

Hi,

The difference between those 2 is that when you configure PortFast on an access-port, if a BPDU is received the port will transition to err-disable state.

On a trunk with PortFast configured, if a BPDU is received, the PortFast will be disabled and the port will enter a full STP mode.

I hope this will help you answer the question with AP's.

[mmanthe]

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@Silviu Pietris wrote:

Hi,

The difference between those 2 is that when you configure PortFast on an access-port, if a BPDU is received the port will transition to err-disable state.

On a trunk with PortFast configured, if a BPDU is received, the PortFast will be disabled and the port will enter a full STP mode.

I hope this will help you answer the question with AP's.

---

I know this is. Very old post - but in the interest of not having mis-information floating around, the 1st statement above is not correct. If a portfast enabled (edge) port receives a BPDU, it will NOT err-disable - not unless you’ve also configured BPDUGARD. if a BPDU is received on an edge port it simply begins the STP process of listening/learning/forwarding...e.g. it stops behaving as a portfast enabled port. 

[CZindy1212]

.... and there is one more case:

you have access switch full of users and you want to provide them redundancy for internet connection, sou you use HSRP for example and now you have switch connected to 2 or more routers with internet links

now, those links between switch and routers are also trunks and the topology is like a triangle with the switch on the tip , omitting PCs for now , at this point the only device taken into consideration is the switch - others don't use STP because routers have configured IP addresses on subinterfaces (each for one VLAN) so they break BRdomain and computers don't care about STP. In this case, you are sure that no routing loop can occur because other devices (all of them are L3) are boundary for that L2 segment and arp requests broadcasted in your LAN stay inside.

What you've just managed to make is faster trunk transition to UP state so after reload of that switch, your users can quickly use network again.