to the default gateway for further routing to their ultimate destination. In this example, the default gateway uses the IP address 192.168.4.1, which is resolved into a MAC address with ARP in the usual way. The destination IP address remains 192.168.12.3, but the next-hop MAC address is that of the gateway, rather than of the ultimate destination. Multi-router In another example, a network with three routers and three hosts is connected to the Internet through Router1. The hosts' addresses are: PC1 10.1.1.100, default gateway 10.1.1.1 PC2 172.16.1.100, default gateway 172.16.1.1 PC3 192.168.1.100, default gateway 192.168.1.96 Router1: Interface 1 5.5.5.2 (public IP) Interface 2 10.1.1.1 Router2: Interface 1 10.1.1.2 Interface 2 172.16.1.1 Router3: Interface 1 10.1.1.3 Interface 2 192.168.1.96 Network mask in all networks: 255.255.255.0 (/24 in CIDR notation). If the routers do not use a routing protocol to discover which network each router is connected to, then the routing table of each router must be set up. Router1 Router2 Router3 Router2 manages its attached networks and default gateway; router 3 does the same; router 1 manages all routes within the internal networks. Accessing internal resources If PC2 (172.16.1.100) needs to access PC3 (192.168.1.100), since PC2 has no route to 192.168.1.100 it will send packets for PC3 to its default gateway (router2). Router2 also has no route to PC3, and it will forward the packets to its default gateway (router1). Router1 has a route for this network (192.168.1.0/24) so router1 will forward the packets to router3, which will deliver the packets to PC3; reply packets will follow the reverse path back to PC2. Accessing external resources If any of the computers try to access a webpage on the Internet, like https://en.wikipedia.org/, the destination will first be resolved to an IP address by using DNS-resolving. The IP-address could be 91.198.174.2. In this example, none of the internal routers know the route to that host, so they will forward the packet through router1's gateway or default route. Every router on the packet's way to the destination will check whether the packet's destination IP-address matches any known network routes. If a router finds a match, it will forward the packet through that route; if not, it will send the packet to its own default gateway. Each router encountered on the way will store the packet ID and where it came from so that it can pass the response packet back to the sender. The