D-Link xStack DES-3528 Series Cli Reference Manual page 521

xStack® DES-3528/DES-3552 Series Layer 2 Fast Ethernet Managed Switch CLI Reference Guide
Configuration:
The configuration logic is listed below:
1. Only when the ARP matches the Source MAC address in Ethernet, the Sender MAC address and Sender IP
address in the 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 DES-3528 series 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 4 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, careful consideration is needed for planning the configuration of the valuable offset_chunks.
In Table-6, you will notice that the Offset_Chunk0 starts from 127th and ends at the 2nd byte. It can also be found that
the offset_chunk is scratched from 1 but not zero.
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 Chunk16 Chunk17 Chunk18
Byte
63 67 71
Byte
64 68 72
Byte
65 69 73
Byte
66 70 74
Table-6: Chunk and Packet offset indicates a completed ARP packet contained in the Ethernet frame, which is
Ethernet Header
Destination Source address
address
(6-byte) (6-byte)
01 02 03 04 05 06 0806
Offset Offset Offset Offset
Chunk3 Chunk4 Chunk5 Chunk6
11 15 19
12 16 20
13 17 21
14 18 22
Offset Offset Offset
Chunk19 Chunk20 Chunk21 Chunk22
75 79 83
76 80 84
77 81 85
78 82 86
the pattern for the calculation of packet offset.
Ethernet H/W type Protocol
type type
(2-byte) (2-byte) (2-byte)
Table – 7: A completed ARP packet contained in Ethernet frame
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 Offset
Chunk23 Chunk24 Chunk25
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)
521
Offset Offset Offset
Chunk10 Chunk11 Chunk12
39 43 47
40 44 48
41 45 49
42 46 50
Offset Offset Offset
Chunk26 Chunk27 Chunk28
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
Chunk29 Chunk30 Chunk31
115 119 123
116 120 124
117 121 125
118 122 126
Target Target
H/W protocol
address
address
(6-byte) (4-byte)