So what happens when we set 1 side to manual trunking
so int g0/0 switchport mode trunk
notice we have to specify an encapsulation
so switchport trunk encapsulation sot1q switchport mode trunk
So I’ve manually configured switch 1 to use trunking
so sh int g0/0 switchport
so this side is configured as a trunk
and is operating as a trunk using 802.1Q
on this switch sh interface trunk
notice it's negotiated to use trunking with 802.1Q
so its currently trunking even though this side was configured for auto.
So sh int g0/0 switchport
This was configured to use DTP or dynamic auto mode
but it became a trunk because the switch on the left was configured as a trunk.
So if you configure 1 side manually
the other side will automatically be configured as a trunk when DTP is used
when this side is configured as an access port
so sh int g0/0 switchport
Notice it was statically configured as an access port
and is operating as an access port.
Negotiation of trunking is off on this side
it’s dynamically configured to use auto
but the operational mode has become static access.
So if 1 side is configured as a trunk statically and the other side is configured
to use either dynamic auto or dynamic desirable a trunk will be formed
but if 1 side is statically configured as an access port.
The DTP side will become an access port.
So the switch can dynamically be configured with the right mode.
you can have a problem where 1 side is configured as access
and 1 side is configured as a trunk port
so you need to either manually configure both sides as a trunk
or manually configure both sides as access or use DTP.
The recommendation is that you manually configure both sides and turn off DTP
So what we will do is do something like this on gigabit 0/0
we’ve configured the encapsulation as dot1q, it’s an access port
but to configure trunking, we type switchport mode trunk
and we would type switchport nonegotiate to disable DTP.
So this is the recommended configuration.
Set your encapsulation to dot1q
set the mode to trunking manually or statically and disable DTP
Now we have to do that on both sides.
So on this side, we will do something similar
sh int g0/0 trunk
notice gigabit 0/0 is configured as a trunk
it’s configured manually or statically, so the mode is on.
It’s currently trunking with the native VLAN set to 1.