A gateway RB may search for an ARP entry of the destination IP address of an IP packet. The gateway RB may generate an Ethernet header based on a VLAN identification and a MAC address in the found ARP entry and a first local MAC address. The gateway RB may generate an Ethernet packet by adding the generated Ethernet header to the IP packet, and send out the Ethernet packet via an egress port in the found ARP entry; wherein the founded ARP entry is generated by the gateway RB based on a received TRILL-encapsulated ARP packet and a VSI on the gateway RB associating with the first local MAC address and the destination IP address of the IP packet belong to the same VLAN.