Interface Vlan

Someone explain to me the relationship between a vlan and the interface vlan's please. The book i studied never covered it. Until recently I figured that the Int vlan was pretty much like a loopback interface, a virtual interface you could ssh to and ping.

While following some labs I had to set a new native vlan to vlan 20 and create int vlan 20 too. I'm assuming that theres more to what the interface vlan does.

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networker050184

Are you familiar with the concept of routing on a stick? It's a similar concept without an external router. It's built in functionality. Imagine someone stuck a router inside your switch and the SVI (Switched Virtual Interface = Vlan Interface) is the same as the sub interface in the router on a stick.

Cisco Inferno

its a make believe interface, aka logical interface. Layer 3 switches use this interface as exit points when receiving packets destined for different VLANs. Think of it as having a make believe router within the switch as opposed to two different networking devices. If you have two devices, the router's interface gets an IP address corresponding to it's VLAN/Subnet. But if you have a Layer 3 device which combines these features, we would still need this VLAN interface to act in place of a Router's interface. These VLAN interfaces, or even a interface on a separate router, is used as the default gateway of clients. (the exit point to get to a different network)

Nik 99

thanks for explaining this one guys. I think I mostly get it now, though I wouldn't always be too sure when a vlan interface would be required to get a configuration working.

Cisco Inferno

Nik 99 wrote: »

thanks for explaining this one guys. I think I mostly get it now, though I wouldn't always be too sure when a vlan interface would be required to get a configuration working.

They are found on Layer 3 Switches. Required for routing on them. Your next question is when and where do you use Layer 3 switches.

Nik 99

Cisco Inferno wrote: »

They are found on Layer 3 Switches. Required for routing on them. Your next question is when and where do you use Layer 3 switches.

Ok. So when and where do you use Layer 3 switches? To my understanding it's not required as you can just use a router and layer 2 switch to achieve the same result.