tailieunhanh - The Illustrated Network- P19

The Illustrated Network- P19:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER 5 Address Resolution Protocol 149 We ll look at the fields of an ARP in detail later. For now note that the ARP request indicated by a 0x0806 in the Ethertype field goes out as a broadcast frame with an all-zero MAC address field. It s looking for the MAC address that goes with IP address winsrv2 the target IP address. The ARP reply frame returns the reply with the correct MAC address plugged into the all-zero field and with the MAC address as the source address in the frame . The results of an ARP pair between the bsdclient host and the lnxserver host is almost the same but not quite. The frame sent in reply to the ARP is smaller than before. bsdclient tethereal -V arp Capturing on em0 Frame 1 42 bytes on wire 42 bytes captured Arrival Time May 5 2008 22 24 Time delta from previous packet seconds Time since reference or first frame seconds Frame Number 1 Packet Length 42 bytes Capture Length 42 bytes Ethernet II Src 00 0e 0c 3b 8f 94 Dst ff ff ff ff ff ff Destination ff ff ff ff ff ff Broadcast Source 00 0e 0c 3b 8f 94 Type ARP 0x0806 Address Resolution Protocol request Hardware type Ethernet 0x0001 Protocol type IP 0x0800 Hardware size 6 Protocol size 4 Opcode request 0x0001 Sender MAC address 00 0e 0c 3b 8f 94 Sender IP address Target MAC address 00 00 00 00 00 00 00 00 00_00 00 00 Target IP address Frame 2 60 bytes on wire 60 bytes captured Arrival Time May 5 2008 22 24 Time delta from previous packet seconds Time since reference or first frame seconds Frame Number 2 Packet Length 60 bytes Capture Length 60 bytes Ethernet II Src 00 d0 b7 1f fe e6 Dst 00 0e 0c 3b 8f 94 Destination 00 0e 0c 3b 8f 94 Source 00 d0 b7 1f fe e6 Type ARP 0x0806 Trailer 000000000000000000000000000000000000 Address Resolution Protocol reply Hardware type Ethernet 0x0001