encapsulation dot1q <vlan id>- confusion

foreverlearningforeverlearning Member Posts: 42 ■■■□□□□□□□
I am confused about what this command does.

Does it 
1) Allow that vlan id to pass through 
2) it encapsulates the original vlan in another vlan?

If it is scenario 1 as explained by my colleague,
how is this command different from switchport mode trunk allowed vlan <vlan id>?
Why is there encapsulation if it is just a vlan being allowed to pass through?

If it is scenario 2,
then is encapsulation dot1q same as qinq terminology? 



  • SpiegelSpiegel Member Posts: 322 ■■■■■□□□□□
    They are both essentially the same same thing. Basically that encapsulation command allows you to use 802.1Q to tag an Ethernet frame with a vlan tag. Cisco used to encapsulate with ISL but that is no longer supported on newer Cisco devices, therefore switchport mode trunk does automatic 802.1Q encasulation.
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