D-Link DWS-3160-24TC DWS-3160 Series CLI Reference Guide - Page 947

DWS-3160 Series Gigabit Ethernet Unified Switch CLI Reference Guide prevent ARP spoofing attack, we will demonstrate here via using Packet Content ACL on the Switch to block the invalid ARP packets which contain faked gateway's MAC and IP binding. Configuration The configuration logic is as follows: • 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.) • 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 127th byte and ends at the 128th byte. It also can be found that the offset chunk is scratched from 1 but not zero. Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Chunk Chunk0 Chunk1 Chunk2 Chunk3 Chunk4 Chunk5 Chunk6 Chunk7 Chunk8 Chunk9 Chunk10 Chunk11 Chunk12 Chunk13 Chunk14 Chunk15 Byte 127 3 7 11 15 19 23 27 31 35 39 43 47 51 55 59 Byte 128 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 Byte 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 Byte 2 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62 Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Offset Chun Chunk1 Chunk1 Chunk1 Chunk1 Chunk2 Chunk2 Chunk2 Chunk2 Chunk2 Chunk2 Chunk2 Chunk2 Chunk2 Chunk2 Chunk3 Chunk3 k 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Byte 63 67 71 75 79 83 87 91 95 99 103 107 111 115 119 123 Byte 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124 Byte 65 69 73 77 81 85 89 93 97 101 105 109 113 117 121 125 Byte 66 70 74 78 82 86 90 94 98 102 106 110 114 118 122 126 Table 6. Chunk and Packet Offset The following table indicates a completed ARP packet contained in Ethernet frame which is the pattern for the calculation of packet offset. 943