Switchport - show vlan internal usage

In legacy IOS versions with older Cisco switches, configuring an interface with the no switchport command and assigning it an IP address would internally create a VLAN (typically in the extended range) and an SVI (Switched Virtual Interface) associated with that VLAN. This was necessary because the switch’s architecture relied on VLANs and SVIs to handle Layer 3 routing, even though the interface was acting as a routed port. The show vlan internal usage command was used to check which VLANs were internally allocated to avoid conflicts when assigning new LAN IDs.

With newer platforms and IOS versions, the architecture has evolved to better integrate Layer 2 and Layer 3 functionality. The new architecture no longer requires the creation of an internal VLAN and SVI when an interface is configured as a routed port. Instead, the routed port is handled more like a traditional router interface, which does not rely on VLANs or SVIs for Layer 3 functionality. Consequently, the show vlan internal usage command has become obsolete.

Links

https://forum.networklessons.com/t/internal-vlans/51561/2?u=lagapidis

https://www.cisco.com/c/en/us/td/docs/ios/lanswitch/command/reference/lsw_book/lsw_s2.html#wp1107373