Native vlan from router to switch

Hi fellas,

I tested a scenario where the Native vlan differs from the router port to
the switch port. I understood that if the NAtive vlan mismatches on a trunk
port , then appropriate trunking wont be formed.
But when i connect my router to a switch and in the router subinterface . I
am having a native vlan of 20 and in the switch port it is having a native
vlan of 10 , but still the trunk is forming perfectly

Can someone correct me
            fa0/1.1 fa0/1
Router1-----------------------------------------------Switch 1

Router 1

inter fa 0/1.1
encap dot1q 20 native
ip add 10.1.1.1 255.255.255.0
no sh

Switch 1

int fa 0/1
enc dot1q 10 native
swi trunk enc dot
swi mo trunk
no sh

But s

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