Layer 2 & Layer 3 switches
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There was a situation that requested to have certain ports to be configured into a specific vlan. (This occurs when there's a new set up with these machines in a different location but require a specfic vlan to get an ip address; trying to be vague in order to not pin point where I work at) I usually use switchport access vlan (vlan name) and call it a day.
However, i noted that the vlan doesn't reside in that switch and when searching for all vlans, it wasn't listed there. Usually I would attempt to trunk the port by checking cdp neighbors but wasn't too comfortable with it. I asked my co worker to help, and our lead mentioned that it's a layer 2 switch and that vlan doesn't reside on that layer 2 network. After back and forth name calling and bashing from the other department who made that original request, they resolved the issue. (my assumption is that they plugged into the layer 3 switch instead).
This is what I know for sure before this hooplah happened: I know that VLANS are layer 2. I know layer 3 has IP addressing.
The switches were: 3560a, and 3750xa
Are the layer 3 switches allows the VLANS to pass traffic across a trunk through routing but the layer 2 switch can't do that feature?
I'm trying to understand this better so when I have to explain it, not only does it make sense to me but I can interpret my answer multiple different ways because not everyone can understand one way of answering a question.
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First off, call the layer 3 switch what it is, a router. They're functionally equivalent. Are you trying to connect to a VLAN at a different location. If so, create a subnet at your end on a VLAN (doesn't have to be the same VLAN number as the other end and then route over whatever means (VPN?) used to reach the other end.
Perhaps you could create a sketch that better shows what you're trying to do.
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@lillianroot
Getting Deja Vu, I feel like I've seen this question posted a while back.(my assumption is that they plugged into the layer 3 switch instead)
I doubt it. They most likely did one of two things... they either spanned the appropriate VLAN out to that switch or put the end-users on a different VLAN and forced them to re-address their equipment.
Are the layer 3 switches allows the VLANS to pass traffic across a trunk through routing but the layer 2 switch can't do that feature?
A layer 3 switch is a switch that also has routing functionality. However, it would need to be configured and implemented properly to actually route traffic. The fact that the switch has layer 3 functionality doesn't necessarily mean it's routing traffic. So, the short answer to your question is no. A layer 3 switch will pass the same VLANs over a trunk that a layer 2 switch will. The difference is layer 3 switches can also do static routing, dynamic routing, etc.
Best practice is for every closet to have unique VLANs. So, if the VLAN you're looking for isn't on the switch, it was probably left off by design. So, someone had to make a decision whether to span that VLAN out to that switch or force the end-users to re-address their equipment on a subnet that exists in that closet.
