tailieunhanh - Practical TCP/IP and Ethernet Networking- P19

Practical TCP/IP and Ethernet Networking- P19: One of the great protocols that has been inherited from the Internet is TCP/IP and this is being used as the open standard today for all network and communications systems. The reasons for this popularity are not hard to find. | 9 TCP IP utilities Objectives When you have completed study of this chapter you should able to apply the following utilities Ping ARP NETSTAT NBTSTAT IPCONFIG WINIPCFG tracert ROUTE Introduction The TCP IP utilities are discussed throughout the book. This section is designed to bring them all together in one section for ease of reference as they are very important in network management and troubleshooting. Most of the older utilities are DOS-based. However more and more Windows-based utilities are becoming available many of them as freeware or shareware. Ping packet Internet groper Pinging is one of the easiest ways to test connectivity across the network and confirm that an IP address is reachable. The DOS ping utility uses ICMP to forward an echo request packet to the destination address. The destination then responds with an ICMP echo response packet. Although the test seems trivial at first sight it is a powerful diagnostic tool and can demonstrate correct operation between the Internet layers of two TCP IPutilities 163 hosts across a WAN regardless of the distance and number of intermediate routers involved. Technically speaking the ping utility can only ping an IP address. This is due to the fact that the ICMP messages are carried within IP datagrams which require the source and destination IP addresses in the header. Without this feature it would have been impossible to ping across a router. If therefore the user does not know the IP address the name resolver on the local host system has to look it up . via the domain name system or in the hosts file. The IP datagram in turn is transported by means of a network interface layer frame . Ethernet which requires in its header the MAC addresses of the source and destination nodes on the local network. If this is not to be found in the ARP cache the ARP protocol is invoked in order to obtain the MAC address. The result of this action the mapping of MAC address against IP address is then .

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