A default gateway is the node in a computer network using the Internet protocol suite that serves as the forwarding host (router) to other networks when no other route specification matches the destination IP address of a packet. Role A gateway is a network node that serves as an access point to another network, often involving not only a change of addressing, but also a different networking technology. More narrowly defined, a router merely forwards packets between networks with different network prefixes. The networking software stack of each computer contains a routing table that specifies which interface is used for transmission and which router on the network is responsible for forwarding to a specific set of addresses. If none of these forwarding rules is appropriate for a given destination address, the default gateway is chosen as the router of last resort. The default gateway can be specified by the route command to configure the node's routing table and default route. In a home or small office environment, the default gateway is a device, such as a DSL router or cable router, that connects the local network to the Internet. It serves as the default gateway for all network devices. Enterprise network systems may require many internal network segments. A device wishing to communicate with a host on the public Internet, for example, forwards the packet to the default gateway for its network segment. This router also has a default route configured to a device on an adjacent network, one hop closer to the public network. Examples Single router The following example shows IP addresses that might be used with an office network that consists of six hosts plus a router. The six hosts addresses are: 192.168.4.3 192.168.4.4 192.168.4.5 192.168.4.6 192.168.4.7 192.168.4.8 The router's inside address is: 192.168.4.1 The network has a subnet mask of: 255.255.255.0 (/24 in CIDR notation) The address range assignable to hosts is from 192.168.4.1 to 192.168.4.254. TCP/IP defines the addresses 192.168.4.0 (network ID address) and 192.168.4.255 (broadcast IP address). The office's hosts send packets to addresses within this range directly, by resolving the destination IP address into a MAC address with the Address Resolution Protocol (ARP) sequence and then encapsulates the IP packet into a MAC frame addressed to the destination host. A packet addressed outside of this range, for this example, addressed to 192.168.12.3, cannot travel directly to the destination. Instead it must be sent