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ARP-RARP protocol

This page covers ARP and RARP protocol basics with example of fields carried in ARP Request and ARP Response message.

This tutorial covers everything one like to know about networking basics including circuit switching vs packet switching, TCP/IP protocol fields, ARP/RARP protocol fields, what is IP address ,what is MAC address, networking devices which include hub, switch, bridge, router, gateway and firewall.

• Circuit Switching vs Packet switching
• LAN vs WAN vs MAN
• What is an IP address
• What is MAC Address
• Basics of OSI and TCP-IP Layers
• What is Hub
• What is Switch
• What is Bridge
• What is Router
• What is Gateway
• Firewall basics
• TCP-IP Packet format
• ARP Protocol format

ARP is Address Resolution Protocol mainly used to determine ethernet address if IP address is known for a node in the network. RARP does reverse of the ARP protocol, it determines IP address if ethernet address is known. Following table mentions ARP protocol fields for ARP request and ARP response. ARP request is the broadcast packet sent to all the PCs. PC whose IP address matches with the one sent in the broadcast packet will respond back to the source PC of the packet with its ethernet address as needed.

Byte position Description ARP Request(Received)-Hex ARP Response(Transmitted)-Hex
1
2
3
4
5
6
Broadcast address(ARP REQ)
Ethernet destination add(ARP RES)
FF
FF
FF
FF
FF
FF
00
A0
C9
22
89
56
7
8
9
10
11
12
Source Ethernet address 00
A0
C9
22
89
56
00
A0
C9
E7
31
45
13
14
Type field 08
06
08
06
15
16
Ethernet 00
01
00
01
17
18
Protocol type 08
00
08
00
19 HA length 06 06
20 PA length 04 04
21
22
Operation 1 ARP REQ
Operation 2 ARP RES
00
01
00
02
23
24
25
26
27
28
Sender Ethernet address 00
A0
C9
22
89
56
00
A0
C9
E7
31
45
29
30
31
32
Sender protocol address AC
12
02
47
AC
12
02
3F
33
34
35
36
37
38
Target Ethernet address 00
00
00
00
00
00
00
A0
C9
22
89
56
39
40
41
42
Target Protocol address AC
12
02
3F
AC
12
02
47
43 to 60 PAD 7E(all bytes,can be any other field also) 7E(all bytes)

Networking related links

What is Bridge
What is Router
What is Gateway
Firewall basics
TCP-IP Packet format
Difference between OSI and TCPIP layers
Difference between TCP UDP

RF and Wireless Terminologies


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