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I understand what a VLAN is and what purpose it serves. However, I'm having a difficult time understanding where VLANs orginate.

Specifically, I know CISCO firewalls, switches, and routers all deal with VLANs: switches are configured with ports on certain VLANs, routers direct traffic between VLANs, and firewall block/allow traffic between VLANs.

But since I'm not an IT professional, where do the VLANs get managed/originated? Say I have VLAN 330 that has addresses between 192.168.1.0/24 and VLAN 331 that has addresses between 192.168.2.0/24. Where is this IP address range determined?

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VLANs are layer-2 broadcast domains, and they have nothing to do with layer-3 (IP). VLANs do not have IP addresses. Using VLANs is like breaking a layer-2 switch into multiple, unconnected layer-2 switches.

Layer-3 interfaces are assigned IP addresses. It is up to the network administrator on how to assign IP addressing. For example, there could be a DHCP server, manually configured interfaces, or both, but that really has nothing to do with VLANs.

Most people will have a one-to-one relationship between the layer-2 VLANs and the layer-3 IP addressing by assigning every layer-3 interface connected to a VLAN with addressing in the same layer-3 network, but that is not a strict requirement. For example, I have seen a large server vendor address its servers with one network for data, one network for administrative access, and one network for a heartbeat between the servers, with all of that on a single VLAN.

Interfaces have IP addresses, VLANs do not.

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Routers and Layer-3 switches manage VLANs. VLAN tags are local to the network. Your network can have VLAN 300 with IP address range 192.168.1.0/24, where as I can create VLAN 300 in my network with an IP address range of 192.168.30.0/25. When you create a VLAN tag of 300, you are creating a Layer-2 network. When you give that VLAN interface of VLAN tag 300 an IP address, you create an SVI (Switch Virtual Interface).

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    Wrong. VLANs are layer 2. Period. They have absolutely nothing to do with layer 3. VLANs do not have IP addresses. You're mixing up VLANs with VLAN Interfaces (SVI).
    – Jesse P.
    Commented Sep 12, 2020 at 15:45
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Layer3 devies liks Routers , Firewalls, multi layered switch , Load balancers , and in layer2 switch VLANs can be created , delete and modification can be done ..

.As per business requirements and network traffic flow in setup VLans can created .

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  • There is no L3 VLAN. The VLAN concept is L2 entirely.
    – Zac67 ♦
    Commented Dec 4, 2020 at 17:33
  • While configuration inter-Vlan routing or SVi configuration L3 Vlan is created for example "switch(config)#interface vlan 10 , switch(config)# ip address 192.168.1.1 255.255.255.0
    – Sagar Uragonda
    Commented Dec 5, 2020 at 2:57
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    You're mixing up VLAN and SVI - a Switch Virtual Interface is an interface to a VLAN.
    – Zac67 ♦
    Commented Dec 5, 2020 at 9:24

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