channel-group 1 and port-channel 1

Switch1:
interface FastEthernet0/10
switchport trunk encapsulation isl
no ip address
channel-group 1 mode desirable
!
interface FastEthernet0/11
switchport trunk encapsulation isl
no ip address
channel-group 1 mode desirable
!
interface FastEthernet0/12
switchport trunk encapsulation isl
no ip address
channel-group 1 mode desirable
!
interface Port-channel1
switchport trunk encapsulation isl

Switch2:
interface FastEthernet0/10
switchport trunk encapsulation isl
no ip address
channel-group 1 mode auto
!
interface FastEthernet0/11
switchport trunk encapsulation isl
no ip address
channel-group 1 mode auto
!
interface FastEthernet0/12
switchport trunk encapsulation isl
no ip address
channel-group 1 mode auto
!
interface Port-channel1
switchport trunk encapsulation isl

I have already configured each interface with :switchport trunk encapsulation isl,,,,why do I need to repeat the same command for Port-Channel1 (boldface) ? What is Port-channel1 here ?

As we know that the above configurations are for etherchannel.

Pitfall:
To ensure that all member interfaces maintain the exact same configuration put them in the channel with the channel-group interface command, then apply all subsequent configuration to the port-channel interface.

Note that for layer 3 EtherChannel configurations, member
interfaces must first be designated as routed interfaces before being
put them in the channel-group.

I am looking for explaination for the above bolded phrase ?

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Comments

Ten9t6

The interface port-channel 1 is automatically created when you did the channel group 1 mode desirable and assigned an interface to it.

What it is saying by they all have to be the same is....all the ports that you assign to the port channel must be the same speed, duplex, native vlan...and so on. If they are not the same you can not group them.

Once you have got the interface port-channel established, you make the changes to it and not the individual interfaces.

An easy way of getting all the ports the same is using the interface range command.

Kenny

zillah

port-channel 1 is automatically created when you did the channel group 1 mode desirable and assigned an interface to it.

Does it become automatically with desirable mode only ?

Once you have got the interface port-channel established, you make the changes to it and not the individual interfaces.

That means by creating channel group ,you can change logical interface (port channel), instead of physical interface (FastEthernet) ?

Comment about this :

Note that for layer 3 EtherChannel configurations, member
interfaces must first be designated as routed interfaces before being
put them in the channel-group