This article summarizes different types of VLAN you can configure on Cisco switches.
There are mainly 3 types of VLANs e.g. Standard VLAN | Extended VLAN | Internal VLAN.
Standard VLANs
-Standard (Normal-range) VLANs are VLANs 1–1005 and can be advertised via VTP versions 1 and 2.
-These VLANs can be configured in VLAN database mode, with the details being stored in the vlan.dat file in Flash.
-VLAN 1 and 1002-1005 are reserved and have following characteristics.
Extended VLANs
-Extended VLAN range is 1006 – 4094.
-These additional VLANs cannot be configured in VLAN database mode, nor stored in the vlan.dat file, nor advertised via VTP. In fact, to configure them, the switch must be in VTP transparent mode. VTP transparent mode stores VLAN configuration in start-up config.
Not all extended VLANs can be used, Some are reserved for “internal” usage.
Extended VLAN can normally only used in one of two cases.
-When VTP is configured in Transparent Mode.
-With VTP Version 3.
Internal VLANs
VLANs reserved for internal applications
e.g. native layer 3 switchports; show vlan internal usage command can be used to view them on cisco IOS-based switches.
When you configure a layer 3 switch port (Routed port) on multi later switch, it assigns that port on one of the extended VLAN on backend and hence we can not use all extended VLANs
Not all platforms agree on the internal range
For real deployments, check the internal allocations; Some allocate ascending, some descending
e.g. VLAN internal allocation policy ascending/descending
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