Upon completion of this lesson, the successful participant will be able to: Understand the need for ARP, understand the cases in which ARP is used, understand the components and interactions in an ARP package, understand the need for RARP. | Chapter 7 ARP and RARP CONTENTS ARP ARP PACKAGE RARP Figure 7-1 ARP and RARP Figure 7-2 Position of ARP and RARP in TCP/IP protocol suite A R P Figure 7-3 ARP operation Figure 7-4 ARP packet Figure 7-5 Encapsulation of ARP packet Figure 7-6:a Four cases using ARP Figure 7-6:b Four cases using ARP Figure 7-6:c Four cases using ARP Figure 7-6:d Four cases using ARP An ARP request is broadcast; an ARP reply is unicast. Example 1 A host with IP address and physical address 0xB23455102210 has a packet to send to another host with IP address and physical address 0xA46EF45983AB. The two hosts are on the same Ethernet network. Show the ARP request and reply packets encapsulated in Ethernet frames. Solution Figure shows the ARP request and reply packets. Note that the ARP data field in this case is 28 bytes, and that the individual addresses do not fit in the 4-byte boundary. Figure 7-7: request Example 1 Figure 7-7: reply Example 1 (Continued) Figure 7-8 . | Chapter 7 ARP and RARP CONTENTS ARP ARP PACKAGE RARP Figure 7-1 ARP and RARP Figure 7-2 Position of ARP and RARP in TCP/IP protocol suite A R P Figure 7-3 ARP operation Figure 7-4 ARP packet Figure 7-5 Encapsulation of ARP packet Figure 7-6:a Four cases using ARP Figure 7-6:b Four cases using ARP Figure 7-6:c Four cases using ARP Figure 7-6:d Four cases using ARP An ARP request is broadcast; an ARP reply is unicast. Example 1 A host with IP address and physical address 0xB23455102210 has a packet to send to another host with IP address and physical address 0xA46EF45983AB. The two hosts are on the same Ethernet network. Show the ARP request and reply packets encapsulated in Ethernet frames. Solution Figure shows the ARP request and reply packets. Note that the ARP data field in this case is 28 bytes, and that the individual addresses do not fit in the 4-byte boundary. Figure 7-7: request Example 1 Figure 7-7: reply Example 1 (Continued) Figure 7-8 Proxy ARP ARP PACKAGE Figure 7-9 ARP components State Queue Attempt Time-out Protocol Addr. Hardware Addr. R 5 900 ACAE32457342 P 2 2 P 14 5 R 8 450 457342ACAE32 P 12 1 F R 9 60 4573E3242ACA P 18 3 Original cache table Example 2 The ARP output module receives an IP datagram (from the IP layer) with the destination address . It checks the cache table and finds that an entry exists for this destination with the RESOLVED state (R in the table). It extracts the hardware address, which is 457342ACAE32, and sends the packet and the address to the data link layer for transmission. The cache table remains the same. Example 3 Twenty seconds later, the ARP output module receives an IP datagram (from the IP layer) with the destination address . It checks the cache table and does not find this destination in the table. The module adds an entry to the table with the state PENDING and the Attempt value
