change port to trunk mode

[vazquez pc-01]

Buenas tardes comunidad, alguien podría ayudarme con una consulta.

Que comandos utilizar para cambiar un puerto de un Switch Catalyst 3560 G48 a modo troncal (trunk)

esta es mi configuración actual en el Switch: (puerto 28 como ejemplo)

interface GigabitEthernet0/28
switchport access vlan 2
spanning-tree portfast
spanning-tree guard loop

deseable:

interface GigabitEthernet0/28
switchport trunk encapsulation dot1q
switchport mode trunk
spanning-tree portfast
spanning-tree guard loop

[Flavio Miranda]

@vazquez pc-01 

The commands is

enable

configure terminal

interface GigabitEthernet0/28

switchport mode trunk

That´s it.

You dont need the command "switchport trunk encapsulation dot1q" in the switch.

And dont use the command "spanning-tree portfast" in a trunk interface.

[vazquez pc-01]

Hi Flavio, thanks for your reply.
I entered the command you told me, but I got the following error:

Sw_Comedor(config-if)#switchport mode trunk

Error:
Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

[Flavio Miranda]

Do this then

enable

configure terminal

default  interface GigabitEthernet0/28

interface GigabitEthernet0/28

switchport mode trunk

[vazquez pc-01]

Thanks Flavio, keep the same error, but the comand defaul it was helpful for us.

[MHM Cisco World]

Error:
Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

This error becuase you dont use 

switchport trunk encapsulation dot1q

MHM

[MHM Cisco World · Accepted solution]

interface GigabitEthernet0/28
switchport trunk encapsulation dot1q <<- optional
switchport mode trunk 

Switchport trunk allow vlan x x x

spanning-tree portfast trunk <<- this need ONLY if you connect SW port to host/server/FW if you connect this SW port to other port then remove this command
spanning-tree guard loop <- this optional

MHM

[vazquez pc-01]

Thanks a lot, it works.