cisco ccna router

cisco ccna router.Sprawl IP address: is a way for the IP protocol to identify a device. An IP address can be assigned to the interface of a host's network card or router. In the network shown in Figure 1-42, hosts A and B are identified by IPv4 addresses 10.0 1 and 10.0.2.2, respectively. IPv4 and IPv6 are two different protocols, and the next section describes information related to IPv4 and IPv6 addresses in more detail.The routing table or routing database: somewhat similar to the MAC address table described in the previous section. The routing table contains two main pieces of information: the destination IP address (or destination network) and the next-hop IP address (the IP address of the next device that should take on the task of forwarding IP packets).Default route: A special record in the routing table that indicates that all packets (regardless of the packet's destination network) are forwarded to the specified next hop.Routed packet: An action performed by a Layer 3 device to forward a packet. When a packet is received from an interface, the network device queries the routing table to see where the packet should be sent. If the relevant record is found in the routing table, the packet is forwarded to the next-hop network device.Router or IP gateway: refers to the Layer 3 device that routes the packets. Such a device will typically have two or more interfaces each connected to a network segment (LAN segment or WAN segment). Although routers are often considered Layer 3 devices, most new routers implement Layer 1.7 of the TCP/IP model. Still, the primary function of a router is to route packets at Layer 3. Both R1 and R2 in Figure 1-42 are routers.Figure 1-43 shows how host A passes information to host Bo46 Chapter 1 Network Protocols and Network Device Basics1-43 Router Routing IP Packet and Routing Table ExampleStep 1. host A encapsulates the data through the layers of protocols that belong to the TCP/IP model, from high to low, up to the IP layer protocols. The IP protocol at the IP layer adds an IP packet header, which is then passed to the link layer and encapsulated into an Ethernet frame by the link layer. The frames are then sent to R1.Step 2. R1 strips the Ethernet header and tail and processes the header of the IP packet. R1 discovers that the destination host of the packet is host B. It needs to query the routing table to discover the next-hop forwarding device. After checking the routing table, R1 learns that the packet can be forwarded to host B through R2. So R1 encapsulates the packet again in a new link-layer frame (for example, a new Ethernet frame) and forwards it to R2.