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Well, I know that's a simple question for the level of this forum, but yet, I didn't found anything on Google, at least not what I want.

I'm studying for CCNA R&S and I just learned about Virtual Interfaces.

And now the question: I have ge0/0 and ge0/0.30. If the physical interface(g0/0) flaps, it automatically happens the same with the virtual one? Or there's a complete independence between them?

Thank you!

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  • BTW, the correct Cisco term is "sub-interface", not "virtual interface".
    – mere3ortal
    Commented Mar 4, 2018 at 3:21
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Commented Apr 1, 2018 at 22:20

2 Answers 2

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A virtual interface will always go down if the corresponding physical interface goes down, it's nothing more than an interface which is used to handle traffic with a specific VLAN tag on the physical interface.

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What you're referring to is actually a sub-interface. A sub-interface is an interface where the name & number of the interface is dependent on another interface. So, gig0/0.30 would be a sub-interface because its number is dependent on gig0/0, which is a physical interface. Another example of a sub-interface would be serial0/0:23 because it's dependent on serial0/0, which is a physical interface.

A virtual interface is one that is purely in software. Examples of virtual interfaces would be loopbacks, tunnels, SVIs, and BVIs. Some virtual interfaces will go down for various reasons, and others won't.

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