Configure a LAN interface as a Layer 3 interface

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A LAN interface cannot be directly configured as Layer 3 interface, and Layer 3 functions are implemented via the VLANIF interface. The VLANIF interface is a logical Layer 3 interface. After an IP address is configured for the VLANIF interface, the device will add the MAC address and VID entry of the VLANIF interface to a MAC address table, and sets the Layer 3 forwarding mark to a bit for the entry. If the destination MAC address of a packet matches the entry, the packet will be forwarded to Layer 3 to implement Layer 3 interconnection between VLANs.

Other related questions:
Does the Ethernet LAN interface card of an AR router provide Layer-2 interfaces or Layer-3 interfaces
All interfaces provided by the Ethernet LAN interface card of an AR router are Layer-2 Ethernet interfaces. Ethernet LAN cards of AR routers include the following models: 8FE1GE: a WSIC card that provides 8 FE interfaces and a GE interface 9ES2: a WSIC card that provides 8 FE electrical interfaces and a GE electrical interface 24GE: an XSIC card that provides 24 GE electrical interfaces 4GE-2S: a WSIC card that provides 4 GE optical interfaces 4ES2G-S: a SIC card that provides 4 GE electrical interfaces 4ES2GP-S: a SIC card that provides 4 GE electrical interfaces

How to configure a Layer 2 interface as a Layer 3 interface on a switch
By default, Ethernet interfaces on switches work as Layer 2 interfaces.Run the undo portswitch command to configure the Ethernet interfaces as Layer 3 interfaces. For switches in V200R003C00 and earlier versions: Only Layer 2 Ethernet interfaces on the S5700HI, S5710EI, and S5710HI can be configured as Layer 3 interfaces. After an Ethernet interface is configured as a Layer 3 interface, the interface cannot be configured with an IP address. For switches in V200R005C00 and later versions: Only Layer 2 Ethernet interfaces on the S5700HI, S5710EI, S5710HI, S5700EI, S5720EI, S5720HI, S6700EI, and S6720EI can be configured as Layer 3 interfaces. After an Ethernet interface is configured as a Layer 3 interface, the interface can be configured with an IP address.

What are the differences of using a Layer 3 interface and a VLANIF interface
On some models of S series switches, you can run the undo portswitch command in the interface view to switch Layer 2 mode to Layer 3 mode. Both Layer 3 interfaces and VLANIF interfaces can provide Layer 3 services. They have the following differences: 1. When an interface works in Layer 2 mode, run Layer 3 services on VLANIF interfaces. Layer 2 services are run on Layer 2 interfaces. 2. After an interface is switched to Layer 3 mode, this interface is similar to a Layer 3 interface of a router, and can only provide Layer 3 services. To run Layer 3 services, use the Layer 3 or VLANIF interface. However, to run both Layer 3 and Layer 2 services on the same interface, use the Layer 2 mode to provide Layer 2 service and VLANIF to provide Layer 3 service.

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