Why does an ARP entry not contain VLAN information

If an ARP entry does not contain VLAN information, the entry contains information about a Layer 3 interface. If an ARP entry contains VLAN information and the interface in the entry is not a sub-interface, the entry contains information about a Layer 2 interface.
Run the display arp command to view ARP entries. For example, the ARP entries in V100R003C00 are as follows:
- When an ARP entry contains VLAN information, a VLAN ID is displayed in the VLAN field in the command output.
- The ARP entry of which the IP address is 10.1.1.2 and the MAC address is 04f9-388d-e685 is dynamically learned from 10GE1/0/3, the VLAN ID is 101, and the remaining lifetime of the entry is 5 minutes.
- The ARP entry of which the IP address is 10.1.1.3 and the MAC address is 0023-0045-0067 is a static entry, the outbound interface is 10GE1/0/3, and the VLAN ID is 101.
display arp network 10.1.1.0 24
ARP Entry Types: D - Dynamic, S - Static, I - Interface
EXP: Expire-time

IP ADDRESS MAC ADDRESS EXP(M) TYPE/VLAN INTERFACE VPN-INSTANCE
------------------------------------------------------------------------------
10.1.1.3 0023-0045-0067 S/101 10GE1/0/3
10.1.1.1 306b-2079-2205 I Vlanif101
10.1.1.2 04f9-388d-e685 5 D/101 10GE1/0/3
------------------------------------------------------------------------------
Total:3 Dynamic:1 Static:1 Interface:1

- When only the ARP entry type is displayed in the TYPE/VLAN field, the ARP entry does not contain VLAN information.
ARP Entry Types: D - Dynamic, S - Static, I - Interface
EXP: Expire-time

IP ADDRESS MAC ADDRESS EXP(M) TYPE/VLAN INTERFACE VPN-INSTANCE
------------------------------------------------------------------------------
172.16.1.3 0023-0045-0069 S 10GE1/0/13
172.16.1.1 306b-2079-2202 I 10GE1/0/13
172.16.1.2 0025-9e95-7c32 3 D 10GE1/0/13
------------------------------------------------------------------------------
Total:3 Dynamic:1 Static:1 Interface:1

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