Layer 3 Forward and ARP Configuration
Chapter 3 Prevent ARP Spoofing Configuration
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Chapter 3 Prevent ARP Spoofing
Configuration
3.1 Overview
3.1.1 ARP (Address Resolution Protocol)
Generally speaking, ARP (RFC-826) protocol is mainly responsible of mapping IP
address to relevant 48-bit physical address, that is MAC address, for instance, IP address
is 192.168.0.1, network card Mac address is 00-03-0F-FD-1D-2B. What the whole
mapping process is that a host computer send broadcast data packet involving IP address
information of destination host computer, ARP request, and then the destination host
computer send a data packet involving its IP address and Mac address to the host, so two
host computers can exchange data by MAC address.
3.1.2 ARP Spoofing
In terms of ARP Protocol design, to reduce redundant ARP data communication on
networks, even though a host computer receives an ARP reply which is not requested by
itself, it will also insert an entry to its ARP cache table, so it creates a possibility
of “ARP
spoofing”. If the hacker wants to snoop the communication between two host computers in
the same network (even if are connected by the switches), it sends an ARP reply packet to
two hosts separately, and make them misunderstand MAC address of the other side as
the hacker host MAC address. In this way, the direct communication is actually
communicated indirectly among the hacker host computer. The hackers not only obtain
communication information they need, but also only need to modify some information in
data packet and forward successfully. In this sniff way, the hacker host computer doesn’t
need to configure intermix mode of network card, that is because the data packet between
two communication sides are sent to hacker host computer on physical layer, which works
as a relay.
3.1.3 How to prevent void ARP Spoofing
There are many sniff, monitor and attack behaviors based on ARP protocol in
networks, and most of attack behaviors are based on ARP spoofing, so it is very important
to prevent ARP spoofing. ARP spoofing accesses normal network environment by
