Technical Reference; Dhcp Snooping Overview - ZyXEL Communications XGS1930-28 User Manual

The following table describes the labels in this screen.
Table 102 Advanced Application > DHCP Snooping > Configure > VLAN > Port
LABEL
VID
Port
Option 82 Profile
Add
Cancel
Clear
Index
VID
Port
Profile Name
Delete
Cancel

26.4 Technical Reference

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

26.4.1 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.
26.4.1.1 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 or 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.
DESCRIPTION
Enter the ID number of the VLAN you want to configure here.
Enter the number of ports to which you want to apply the specified DHCP option 82 profile.
You can enter multiple ports separated by (no space) comma (,) or hyphen (–). For
example, enter "3–5" for ports 3, 4, and 5. Enter "3,5,7" for ports 3, 5, and 7.
Select a pre-defined DHCP option 82 profile that the Switch applies to the specified ports in
this VLAN. The Switch adds the information (such as slot number, port number, VLAN ID and/
or system name) specified in the profile to DHCP requests that it broadcasts to the DHCP
VLAN, if specified, or VLAN. You can specify the DHCP VLAN in the DHCP Snooping
Configure screen (see Section 26.3 on page
The profile you select here has priority over the one you select in the DHCP Snooping >
Configure > VLAN screen.
Click this to create a new entry or to update an existing one.
This saves 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 above based on the last selected entry or, if not applicable, to
clear the fields above.
Click Clear to reset the fields to the factory defaults.
This field displays a sequential number for each entry. Click an index number to change the
settings.
This field displays the VLAN to which the ports belong.
This field displays the ports to which the Switch applies the settings.
This field displays the DHCP option 82 profile that the Switch applies to the ports.
Select the entries that you want to remove in the Delete column, then click the Delete
button to remove the selected entries from the table.
Click this to clear the Delete check boxes above.
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213).