ZyXEL Communications OLT2406, User Manual

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Chapter 77 IP Source Guard
OLT2406 User’s Guide
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• System name (Up to 32 bytes)
This information is stored in an Agent Information field in the option 82 field of the DHCP headers of client
DHCP request frames. See
Chapter 82 on page 590 for more information about DHCP relay option 82.
When the DHCP server responds, the OLT removes the information in the Agent Information field before
forwarding the response to the original source.
You can configure this setting for each source VLAN. This setting is independent of the DHCP relay
settings (
Chapter 82 on page 590 ).
77.1.1.4 Configuring DHCP Snooping
Follow these steps to configure DHCP snooping on the OLT.
1
Enable DHCP snooping on the OLT.
2
Enable DHCP snooping on each VLAN, and configure DHCP relay option 82.
3
Configure trusted and untrusted ports, and specify the maximum number of DHCP packets that each
port can receive per second.
4
Configure static bindings.
77.1.2 ARP Inspection Overview
Use ARP inspection to filter unauthorized ARP packets on the network. This can prevent many kinds of
man-in-the-middle attacks, such as the one in the following example.
Figure 273 Example: Man-in-the-middle Attack
In this example, computer B tries to establish a connection with computer A . Computer X is in the same
broadcast domain as computer A and intercepts the ARP request for computer A . Then, computer X
does the following things:
• It pretends to be computer A and responds to computer B .
• It pretends to be computer B and sends a message to computer A .
As a result, all the communication between computer A and computer B passes through computer X .
Computer X can read and alter the information passed between them.