Here is the scoop! Trunks ONLY CARRY TAGGED FRAMES, that's what trunks
were designed to do. the purpose of a trunk is to be able to TRANSFER DATA
FROM DIFFERENT VLANs. The reason the frames are tagged before they traverse
the trunk is so that when it gets to the other side of the trunk, the switch can
READ THE TAG AND DETERMINE WHICH VLAN THE FRAME BELONGS TO and then
forward it on to that VLAN.
Now the native VLAN. The purpose of the native VLAN is so that if untagged data finds its way traversing the trunk (usually because it entered the trunk somewhere in the middle, most likely from a connected hub so that the frame could not be tagged by the switch before entering the trunk), when that untagged frame gets to either end of the trunk, the switch then reads the frame sees that it is an untagged frame that ended up on the trunk and sends that untagged frame to the VLAN that has been assigned as the native VLAN.
Remember, TRUNKS ONLY CARRY TAGGED FRAMES, all untagged frames goes to the native vlan. So to answer your question, if VLAN1 hits the trunk, it too will be tagged, so that the switch on the other side of the trunk can determine which VLAN the frame belongs to and forward the frame to the appropriate VLAN.
For more discussion on this topic, take a look at https://learningnetwork.cisco.com/thread/2217.
Now the native VLAN. The purpose of the native VLAN is so that if untagged data finds its way traversing the trunk (usually because it entered the trunk somewhere in the middle, most likely from a connected hub so that the frame could not be tagged by the switch before entering the trunk), when that untagged frame gets to either end of the trunk, the switch then reads the frame sees that it is an untagged frame that ended up on the trunk and sends that untagged frame to the VLAN that has been assigned as the native VLAN.
Remember, TRUNKS ONLY CARRY TAGGED FRAMES, all untagged frames goes to the native vlan. So to answer your question, if VLAN1 hits the trunk, it too will be tagged, so that the switch on the other side of the trunk can determine which VLAN the frame belongs to and forward the frame to the appropriate VLAN.
For more discussion on this topic, take a look at https://learningnetwork.cisco.com/thread/2217.
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