Catalyst 3750 configuration question (trunk + port channel)

[d.camboni]

Hi guys,

I have a doubt about trunk and port-channel:

Which configuration is correct to do a port-channel with trunk between two Gi ports ?

Configuration a)

interface Port-channel1
 switchport trunk encapsulation dot1q
 switchport mode trunk

!

interface GigabitEthernet1/0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 channel-group 1 mode active
!
interface GigabitEthernet1/0/2
 switchport trunk encapsulation dot1q
 switchport mode trunk
 channel-group 1 mode active
!

Configuration b)

interface Port-channel1

!

interface GigabitEthernet1/0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 channel-group 1 mode active
!
interface GigabitEthernet1/0/2
 switchport trunk encapsulation dot1q
 switchport mode trunk
 channel-group 1 mode active
!

Maybe both are correct but I don't know the difference...

thanks Davide

[Reza Sharifi]

Hi,

a is correct.  When you configure a portchannel, you apply all the configs under the portchannel interface and the physical interfaces inherit the config from the portchannel.

for example

if you want to configure all the ports as trunk, you add the config to the portchannel and then physical ports inherit that.  No need to add the command manually to each physical interface.

HTH

[d.camboni]

If I understand I don't need to configure trunk in physical interface:

The correct configuration is:

interface Port-channel1
 switchport trunk encapsulation dot1q
 switchport mode trunk

!

interface GigabitEthernet1/0/1
 channel-group 1 mode active
!
interface GigabitEthernet1/0/2
  channel-group 1 mode active
!

[Reza Sharifi · Accepted solution]

That is correct.  Once you configure it under the portchannel, the same command should show up under the physical links.

HTH