A packet forwarding method, apparatus, and system in which a host receives a first packet sent by a gateway, and parses the first packet to obtain a source IP address and a source MAC address from the first packet; queries a host cache table, when a mapping relationship between the source IP address and the source MAC address does not exist in the host cache table, saves the mapping relationship between the source IP address and the source MAC address in the host cache table; the host generates a response packet according to the first packet, and queries the host cache table to acquire a first destination MAC address corresponding to a first destination IP address that is in the response packet; and forwards, according to the first destination MAC address, the response packet to an external network by using the gateway.