Related How To Notes; Dhcp Snooping; Minimum Configuration - Allied Telesis AT-8600 Series How To Use Manual

Related How To Notes

The following How To Note describes DHCP snooping on AT-9900, x900-48 and AT-8948
series switches:
How To Use DHCP Snooping, Option 82, and Filtering on AT-9900 and x900-48 Series Switches
The following How To Notes also use DHCP snooping in their solutions:
How To Use MAC-Forced Forwarding with DHCP Snooping to Create Enhanced Private VLANs
How To Create A Secure Network With Allied Telesis Managed Layer 3 Switches
How To Use DHCP Snooping and ARP Security to Block ARP Poisoning Attacks
How To Notes are available from the library at
howto.aspx.

DHCP snooping

DHCP snooping forces all DHCP packets to be sent up to the switch CPU before forwarding.
The switch CPU then keeps a database of the IP addresses that are currently allocated to
downstream clients and the switch ports that the relevant clients are attached to.
Note:
DHCP snooping performs two main tasks:
Keeping a record of which IP addresses are currently allocated to hosts downstream of
the ports on the switch.
Deciding which packets are candidates for having Option 82 information inserted, and
actively filtering out packets that are deemed to be invalid DHCP packets (according to
criteria described below).
Note:

Minimum configuration

The following output shows the minimum configuration required to use DHCP snooping and
provide filtered connectivity. With this configuration a client will be able to receive a DHCP
address, and access the IP network. If the client manually changes its IP, it will not be
permitted access to the IP network. The administrator will also be able to see the current
valid entries in the DHCP snooping database.
# DHCP Snooping configuration
enable dhcpsnooping
set dhcpsnooping port=24 trusted=yes
Page 3 | AlliedWare™ OS How To Note: DHCP Snooping on Rapier-style switches
The switch CPU does not store a history log. The DHCP server does this.
Option 82 must be enabled separately.
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DHCP snooping