ccna renew

ccna renew.An example RARP is shown in the lower half of Figure 5.2. In this example, the PC-D does not have an IP address and wants to obtain one. To do so, it generates a data link layer broadcast (FF:FF:FF:FF:FF:FF:FF) that encapsulates the RARP request. It is assumed here that the RARP request is associated with BOOTP; if there is a BOOTP server in the network segment and that server has an IP address available for assignment to the requesting device, it will respond. In this example, the BOOTP server (10.1.1.5) has an address available for assignment to PC.5.2.3 ICMPICMP is used to send error and control messages between TCP/IP devices at the Internet layer OICMP was originally standardized in RFC 792 and defines a number of messages that a device can generate or respond to ICMP messages are encapsulated in IP datagrams (packets) ICMP messages include: address answer, address request, destination device unreachable, return, return answer message answer, message request, parameter question, redirect, subnet mask request, timeout, timestamp, and timestamp answer.One of the most common applications that use ICMP is ping,which uses a variety of ICMP messages, including sendback, sendback request, and target device unreachable. ping is used to test whether the target device is available. To do this, the source device generates ICMP sendback packets; if the target device is available, it responds with a sendback reply packet. If the intermediate router does not know how to get to the target device, it will respond with a target device unreachable message. If the router knows how to get to the target device, but the target device does not respond to the sendback request, you will see a request timeout message. traceroute applications (sometimes called traces) list the IP addresses of the routers passed on the way to the target device, thus indicating the path of the packet to the target device. Some traceroute applications use ICMP messages, while others use UDP to transport messages. These tools are discussed in more detail in the next section and in Chapter 16.Two common applications that use ICMP are ping and tracerouteoping use ICMP send-back messages to check connectivity to remote devices.ICMP messages are encapsulated in IP packets. If the intermediate router does not know how to get to the target device, it will use theIf the intermediate router does not know how to get to the target device, it will respond with an ICMP target device unreachable message.Authentication Target 5.035.3 TCP/IP Tools forVarious tools are available on the device to check the IP configuration and connectivity to other devices. This section discusses tools that can be used on a Windows PC: ipconfig, ping, tracert, and arp.