C613-50631-01 Rev A Command Reference for IE340 Series 2561
AlliedWare Plus™ Operating System - Version 5.5.3-0.x
DHCP SNOOPING COMMANDS
IP
DHCP SNOOPING
ip dhcp snooping
Overview Use this command to enable DHCP snooping on one or more VLANs.
Use the no variant of this command to disable DHCP snooping on the VLANs.
Syntax
ip dhcp snooping
no ip dhcp snooping
Default DHCP snooping is disabled on VLANs by default.
Mode Interface Configuration (VLANs)
Usage notes Enabling DHCP snooping
For DHCP snooping to operate on a VLAN, you must:
• enable the service on the switch by using the service dhcp-snooping
command, and
• enable DHCP snooping on the particular VLAN by using the ip dhcp
snooping command, and
• if there is an external DHCP server, configure the port connected to the
server as a trusted port, by using the ip dhcp snooping trust command
Disabling DHCP snooping
Use no service dhcp-snooping to disable DHCP snooping.
Disabling DHCP snooping removes all DHCP snooping configuration from the
running configuration, except for:
• any DHCP snooping maximum bindings settings (ip dhcp snooping
max-bindings), and
• any additional DHCP snooping-based ACLs you have created for filtering on
untrusted ports.
You must remove any such additional DHCP snooping-based ACLs, using the no
access-group command. This is because these ACLs block all traffic except for
traffic that matches DHCP snooping entries. Once you have disabled DHCP
snooping, these ACLs will block all traffic. Note that if you disable DHCP snooping
on particular VLANs (using the no ip dhcp snooping command), you need to
make sure you remove any such additional ACLs that apply to those VLANs.
If you re-enable the service, the switch repopulates the DHCP snooping database
from the dynamic lease entries in the database backup file (see the ip dhcp
snooping database command). It also updates the lease expiry times.
Examples To enable DHCP snooping on VLANs 2 to 4, use the commands:
awplus# configure terminal
awplus(config)# interface vlan2-vlan4
awplus(config-if)# ip dhcp snooping
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