Technical Reference; Dhcp Snooping Overview - ZyXEL Communications GS2210 Series User Manual

Table 117 Advanced Application > IP Source Guard > IPv6 DHCP Trust Setup
LABEL
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Trusted state
Apply
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26.19 Technical Reference

This section provides technical background information on the topics discussed in this chapter.

26.19.1 DHCP Snooping Overview

Use DHCP snooping to filter unauthorized DHCP packets on the network and to build the binding
table dynamically. This can prevent clients from getting IP addresses from unauthorized DHCP
servers.
26.19.1.1 Trusted vs. Untrusted Ports
Every port is either a trusted port or an untrusted port for DHCP snooping. This setting is
independent of the trusted/untrusted setting for ARP inspection. You can also specify the maximum
number for DHCP packets that each port (trusted or untrusted) can receive each second.
Trusted ports are connected to DHCP servers or other switches. The Switch discards DHCP packets
from trusted ports only if the rate at which DHCP packets arrive is too high. The Switch learns
dynamic bindings from trusted ports.
Note: If DHCP is enabled and there are no trusted ports, DHCP requests will not succeed.
Untrusted ports are connected to subscribers. The Switch discards DHCP packets from untrusted
ports in the following situations:
• The packet is a DHCP server packet (for example, OFFER, ACK, or NACK).
• The source MAC address and source IP address in the packet do not match any of the current
bindings.
Chapter 26 IP Source Guard
DESCRIPTION
Settings in this row apply to all ports.
Use this row only if you want to make some settings the same for all ports. Use this row
first to set the common settings and then make adjustments on a port-by-port basis.
Note: Changes in this row are copied to all the ports as soon as you make them.
Select whether this port is a trusted port (Trusted) or an untrusted port (Untrusted).
Trusted ports are connected to DHCPv6 servers or other switches.
Untrusted ports are connected to subscribers, and the Switch discards DHCPv6 packets
from untrusted ports in the following situations:
• The packet is a DHCPv6 server packet (for example, ADVERTISE, REPLY, or RELAY-
REPLY).
• The source MAC address and source IP address in the packet do not match any of the
current bindings.
Click Apply to save your changes to the Switch's run-time memory. The Switch loses
these changes if it is turned off or loses power, so use the Save link on the top navigation
panel to save your changes to the non-volatile memory when you are done configuring.
Click this to reset the values in this screen to their last-saved values.
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