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xStack DGS-3200 Series Layer 2 Managed Gigabit Ethernet Switch Web UI Reference Guide
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 the 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
127 3 7
Byte
Byte 128 4 8
1 5 9
Byte
Byte 2 6 10
Offset Offset Offset Offset
Chunk Chunk16 Chunk17 Chunk18
Byte 63 67 71
64 68 72
Byte
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 an Ethernet Frame
Ethernet Header
Destination Source Address
Address
(6-byte) (6-byte)
01 02 03 04 05 06
Offset Offset Offset Offset
Chunk3 Chunk4 Chunk5 Chunk6
11 15 19 23
12 16 20 24
13 17 21 25
14 18 22 26
Offset Offset Offset Offset
Chunk19 Chunk20 Chunk21 Chunk22
75 79 83 87
76 80 84 88
77 81 85 89
78 82 86 90
Ethernet H/W Protocol
Type Type Type
(2-byte) (2-byte) (2-byte)
0806
th
byte and ends at the 128
Offset Offset Offset Offset
Chunk7 Chunk8 Chunk9 Chunk10
27 31 35
28 32 36
29 33 37
30 34 38
Offset Offset Offset
Chunk23 Chunk24 Chunk25 Chunk26
91 95 99
92 96 100
93 97 101
94 98 102
ARP
H/W Protocol Operation
Address Address
Length Length
(1-byte) (1-byte) (2-byte)
282
th
byte. It also can be found that
Offset Offset Offset
Chunk11 Chunk12 Chunk13
39 43 47 51
40 44 48 52
41 45 49 53
42 46 50 54
Offset Offset Offset Offset
Chunk27 Chunk28 Chunk29
103 107 111 115
104 108 112 116
105 109 113 117
106 110 114 118
Sender Sender Protocol
H/W Address
Address
(6-byte) (4-byte)
0a5a5a5a
(10.90.90.90)
Offset Offset
Chunk14 Chunk15
55 59
56 60
57 61
58 62
Offset Offset
Chunk30 Chunk31
119 123
120 124
121 125
122 126
Target Target
H/W Protocol
Address Address
(6-byte) (4-byte)