Why proxy ARP does not take effect after the arp-proxy enable command is used on an interface

Proxy ARP is classified into routed proxy ARP, intra-VLAN proxy ARP, and inter-VLAN proxy ARP, which are configured by arp-proxy enable, arp-proxy inner-sub-vlan-proxy enable, and arp-proxy inter-sub-vlan-proxy enable. Each proxy function takes effect in corresponding scenarios.

Routed proxy ARP

Routed proxy ARP takes effect when the destination IP address in the received ARP request packet and the IP address of the inbound interface are in different network segments, but there is a route to the destination IP address and the outbound and inbound interfaces of the route are different. A device uses its MAC address as the source MAC address to return ARP response packets.

Intra-VLAN proxy ARP

Intra-VLAN proxy ARP takes effect when the destination IP address of the received ARP request packet and the IP address of the inbound interface are in the same network segment.

Inter-VLAN proxy ARP

Inter-VLAN proxy ARP is similar to intra-VLAN proxy ARP. Inter-VLAN proxy ARP takes effect when being applied to the super VLAN. If the destination IP address of the received ARP request packet and the IP address of the inbound interface are in the same network segment, inter-VLAN proxy ARP takes effect. If the source and destination are in the same VLAN, inter-VLAN proxy ARP is not required.

Regardless of whether proxy ARP is used, the source IP address of the received ARP request packet and the IP address of the inbound interface must be in the same network segment.

Intra-VLAN proxy is often used; therefore, the arp-proxy inner-sub-vlan-proxy enable command is used more often than the arp-proxy enable command.

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