Dhcp Snooping Configuration Guidelines; Dhcp Snooping Configuration Restrictions And Guidelines - Cisco 7604 Configuration Manual

Chapter 37 Configuring DHCP Snooping

DHCP Snooping Configuration Restrictions and Guidelines

These sections provide DHCP snooping configuration restrictions and guidelines:
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DHCP Snooping Configuration Restrictions
When configuring DHCP snooping, note these restrictions:
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DHCP Snooping Configuration Guidelines

When configuring DHCP snooping, follow these guidelines:
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OL-4266-08
DHCP Snooping Configuration Restrictions, page 37-7
DHCP Snooping Configuration Guidelines, page 37-7
Minimum DHCP Snooping Configuration, page 37-8
The PFC2 does not support DHCP snooping.
With releases earlier than Release 12.2(18)SXF5, the DHCP snooping database stores a maximum
of 512 bindings. If the database attempts to add more than 512 DHCP bindings, all bindings are
removed from the database.
With Release 12.2(18)SXF5 and later releases, the DHCP snooping database stores at least 8,000
bindings.
When DHCP snooping is enabled, these Cisco IOS DHCP commands are not available on the router:
ip dhcp relay information check global configuration command
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ip dhcp relay information policy global configuration command
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ip dhcp relay information trust-all global configuration command
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ip dhcp relay information option global configuration command
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ip dhcp relay information trusted interface configuration command
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If you enter these commands, the router returns an error message, and the configuration is not
applied.
DHCP snooping is not active until you enable the feature on at least one VLAN, and enable DHCP
globally on the router.
Before globally enabling DHCP snooping on the router, make sure that the devices acting as the
DHCP server and the DHCP relay agent are configured and enabled.
For DHCP server configuration information, refer to "Configuring DHCP" in the Cisco IOS IP and
IP Routing Configuration Guide at:
http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfdhcp.html
If a Layer 2 LAN port is connected to a DHCP server, configure the port as trusted by entering the
ip dhcp snooping trust interface configuration command.
If a Layer 2 LAN port is connected to a DHCP client, configure the port as untrusted by entering the
no ip dhcp snooping trust interface configuration command.
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
DHCP Snooping Configuration Restrictions and Guidelines
37-7