I wanted to know if the command: "switchport trunk encapsualtion dot1q" is always required first before one configures an interface hardcoded as a trunk? I know that by default on most switches the interfaces are set to "auto negotiate" but not at all switch models.Thank you
If the switch supports different types of encapsuplations, then you could also use sw tr en isl. You can have ISL vs. dot1q. I never have, but sure they are out there.
it all depends if your switch model supports the ISL protocol too, 2950 doesn't so no need for this command but 3550,3560 and 3750 do so you'll need it indeed in these cases.
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you first need to set the mode to trunk or you can use auto if the other end is already a configured trunk on another switch but if you know it needs to be a trunk id just set it as trunk .
so you run sw mode trunk as is mentioned above. you then need to run sw trunk encap dot1q/isl I'd use dot1q but its up to you just remember it must be the same on both ends. you then need to set the native vlan eg sw trunk native vlan 10, again must be the same at each end, and finally the vlans that are permitted on the trunk. normally unless I have a reason not to I just explicitly allow any vlan so sw trunk allowed vlan all
Hope this helps!!