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examine-dhcp

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 9.0 for EX Series switches.

Description

Enable DHCP snooping on all VLANs or on the specified VLAN.

Note

If you configure DHCP for all VLANs and you enable a different port security feature on a specific VLAN, you must also explicitly enable DHCP snooping on that VLAN. Otherwise, the default value of no DHCP snooping applies to that VLAN.

  • examine-dhcp—Enable DHCP snooping.

  • no-examine-dhcp—Disable DHCP snooping.

When DHCP snooping is enabled, the switch logs DHCP packets (DHCPOFFER, DHCPDECLINE, DHCPACK, and DHCPNAK packets) that it receives on untrusted ports. You can monitor the log for these messages, which can signal the presence of a malicious DHCP server on the network.

Tip

For private VLANs (PVLANs), enable DHCP snooping on the primary VLAN. If you enable DHCP snooping only on a community VLAN, DHCP messages coming from PVLAN trunk ports are not snooped.

The remaining statement is explained separately.

Default

Disabled.

Required Privilege Level

system—To view this statement in the configuration.

system-control—To add this statement to the configuration.