switch port

[ebraa2401]

Hi 

I would like to ask

why Cisco create dynamic auto switch-port mode if dynamic desirable founded ?

where we use dynamic auto ?

[Venkatesh Perumal]

Difference between Dynamic Desirable and dynamic auto

Dynamic Desirable

by default dynamic desirable meaning that if you connect one switch to another switch it will automatically negotiate a trunk.

a default 3550 port will create a trunk when connected to any other port except one that is configured as a access port.

Dynamic auto

A default 3560 port will create a trunk when connected to any other port except one that is configured as a access port OR a port configured as “switchport mode dynamic auto.”

find the some of  the combination which will help you understand easily .

Switchport Mode	Access	Dynamic Desirable	Dynamic Auto	Trunk
Access	No Trunk	No Trunk	No Trunk	No Trunk
Dynamic Auto	No Trunk	Trunk	No Trunk	Trunk
Dynamic Desirable	No Trunk	Trunk	Trunk	Trunk
Trunk	No Trunk	Trunk	Trunk	Trunk

DTP configurations:

Access

Switch(config-if)# switchport mode access

Dynamic Auto

Switch(config-if)# switchport mode dynamic auto
Dynamic Desirable

Switch(config-if)# switchport mode dynamic desirable

Trunk port

Switch(config-if)# switchport mode trunk

https://ccnatoccie.wordpress.com/2010/12/16/difference-between-dynamic-desirable-and-dynamic-auto/

http://bradhedlund.com/2007/11/27/switchport-configurations-explained/

https://learningnetwork.cisco.com/thread/5882

regards,

-Do rate helpful posts.

[ebraa2401]

i know that but why Cisco created dynamic auto ? dynamic desirable Enough we don't need dynamic auto

[InayathUlla Sharieff]

switchport mode dynamic auto - allows the port to negotiate DTP if the other side is set to trunk or desirable. Otherwise it will become an access port

question:why Cisco created dynamic auto ?

Answer:- that was created who doesnt want to use the configuration mode of desirable were in the port goes out for negotiating.

HTH

Regards

Inayath

[Ganesh Hariharan]

i know that but why Cisco created dynamic auto ? dynamic desirable Enough we don't need dynamic auto

Hello,

Auto keyword has some significance , Like if the port is connected with a third party device and they don't want to make special changes as per your need. In that case dynamic auto plays a good role which allows the port to negotiate DTP if the other side is set to trunk or desirable. Otherwise it will become an access port.

Which is also explained by InayathUlla.

Hope it Helps..

-GI