D-Link DGS-3200 Series User Manual page 248

Configuration
The configuration logic is as follows:
1. Only if the ARP matches Source MAC address in Ethernet, Sender MAC address and Sender IP address in ARP protocol can
pass through the switch. (In this example, it is gateway's ARP.)
2. The switch will deny all other ARP packets which claim they are from the gateway's IP.
The design of Packet Content ACL on the Switch enables users to inspect any offset chunk. An offset chunk is a 4-byte block in a
HEX format, which is utilized to match the individual field in an Ethernet frame. Each profile is allowed to contain up to a
maximum of four offset chunks. Furthermore, only one single profile of Packet Content ACL can be supported per switch. In
other words, up to 16 bytes of total offset chunks can be applied to each profile and a switch. Therefore, a careful consideration is
needed for planning and configuration of the valuable offset chunks.
In Table-6, you will notice that the Offset_Chunk0 starts from the 127
the offset chunk is scratched from 1 but not zero.
Table-6: Chunk and packet offset
Offset Offset Offset Offset
Chunk Chunk0 Chunk1 Chunk2
Byte 127 3 7
Byte 128 4 8
Byte 1 5 9
Byte 2 6 10
Offset Offset Offset Offset
Chunk Chunk15 Chunk16 Chunk17
Byte 63 67 71
Byte 64 68 72
Byte 65 69 73
Byte 66 70 74
The following table indicates a completed ARP packet contained in Ethernet frame which is the pattern for the calculation of
packet offset.
Table-7: A completed ARP packet contained in Ethernet frame
Ethernet Header
Destination Source address
address
(6-byte) (6-byte)
01 02 03 04 05 06
DGS-3200 Series Layer 2 Gigabit Ethernet Managed Switch
Offset Offset Offset Offset
Chunk3 Chunk4 Chunk5 Chunk6
11 15 19
12 16 20
13 17 21
14 18 22
Offset Offset Offset Offset
Chunk18 Chunk19 Chunk20 Chunk21
75 79 83
76 80 84
77 81 85
78 82 86
Ethernet H/W type Protocol
type type
(2-byte) (2-byte) (2-byte)
0806
th
byte and ends at the 128
Offset Offset Offset
Chunk7 Chunk8 Chunk9
23 27 31 35
24 28 32 36
25 29 33 37
26 30 34 38
Offset Offset Offset
Chunk22 Chunk23 Chunk24
87 91 95 99
88 92 96 100
89 93 97 101
90 94 98 102
H/W Protocol Operation
address address
length length
(1-byte) (1-byte) (2-byte)
234
th
byte. It also can be found that
Offset Offset Offset
Chunk10 Chunk11 Chunk12
39 43 47
40 44 48
41 45 49
42 46 50
Offset Offset Offset
Chunk25 Chunk26 Chunk27
103 107 111
104 108 112
105 109 113
106 110 114
ARP
Sender Sender protocol
H/W address
address
(6-byte) (4-byte)
0a5a5a5a
(10.90.90.90)
Offset Offset Offset
Chunk13 Chunk14 Chunk15
51 55 59
52 56 60
53 57 61
54 58 62
Offset Offset Offset
Chunk28 Chunk129 Chunk30
115 119 123
116 120 124
117 121 125
118 122 126
Target Target
H/W protocol
address address
(6-byte) (4-byte)