HP Cisco Catalyst Blade Switch 3020 Cisco Catalyst Blade Switch 3020 for HP So - Page 371
DHCP Snooping Configuration Guidelines
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Chapter 17 Configuring DHCP Features Configuring DHCP Features Table 17-1 Default DHCP Configuration (continued) Feature DHCP relay agent forwarding policy Default Setting Replace the existing relay agent information2 DHCP snooping enabled globally Disabled DHCP snooping information option Enabled DHCP snooping option to accept packets on untrusted input interfaces3 Disabled DHCP snooping limit rate None configured DHCP snooping trust Untrusted DHCP snooping VLAN Disabled DHCP snooping MAC address verification Enabled 1. The switch responds to DHCP requests only if it is configured as a DHCP server. 2. The switch relays DHCP packets only if the IP address of the DHCP server is configured on the SVI of the DHCP client. 3. Use this feature when the switch is an aggregation switch that receives packets with option-82 information from an edge switch. DHCP Snooping Configuration Guidelines These are the configuration guidelines for DHCP snooping. • You must globally enable DHCP snooping on the switch. • DHCP snooping is not active until DHCP snooping is enabled on a VLAN. • Before globally enabling DHCP snooping on the switch, make sure that the devices acting as the DHCP server and the DHCP relay agent are configured and enabled. • When you globally enable DHCP snooping on the switch, these Cisco IOS commands are not available until snooping is disabled. If you enter these commands, the switch returns an error message, and the configuration is not applied. - ip dhcp relay information check global configuration command - ip dhcp relay information policy global configuration command - ip dhcp relay information trust-all global configuration command - ip dhcp relay information trusted interface configuration command • Before configuring the DHCP snooping information option on your switch, be sure to configure the device that is acting as the DHCP server. For example, you must specify the IP addresses that the DHCP server can assign or exclude, or you must configure DHCP options for these devices. • When configuring a large number of circuit IDs on a switch, consider the impact of lengthy character strings on the NVRAM or the flash memory. If the circuit-ID configurations, combined with other data, exceed the capacity of the NVRAM or the flash memory, an error message appears. • If the DHCP relay agent is enabled but DHCP snooping is disabled, the DHCP option-82 data insertion feature is not supported. • If a switch port is connected to a DHCP server, configure a port as trusted by entering the ip dhcp snooping trust interface configuration command. OL-8915-01 Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide 17-7
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