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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 19 Configuring DHCP Features and IP Source Guard
Configuring DHCP Features
• Enabling DHCP Snooping on Private VLANs, page 19-13
• Enabling the Cisco IOS DHCP Server Database, page 19-13
• Enabling the DHCP Snooping Binding Database Agent, page 19-14
Default DHCP Configuration
Table 19-1 shows the default DHCP configuration.
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.
Ta ble 19-1 Default DHCP Configuration
Feature Default Setting
DHCP server Enabled in Cisco IOS software, requires configuration
1
1. The switch responds to DHCP requests only if it is configured as a DHCP server.
DHCP relay agent Enabled
2
2. The switch relays DHCP packets only if the IP address of the DHCP server is configured on the SVI of the DHCP client.
DHCP packet forwarding address None configured
Checking the relay agent information Enabled (invalid messages are dropped)
2
DHCP relay agent forwarding policy Replace the existing relay agent information
2
DHCP snooping enabled globally Disabled
DHCP snooping information option Enabled
DHCP snooping option to accept packets on
untrusted ingress interfaces
3
3. Use this feature when the switch is an aggregation switch that receives packets with option-82 information from an edge switch.
Disabled
DHCP snooping limit rate None configured
DHCP snooping trust Untrusted
DHCP snooping VLAN Disabled
DHCP snooping MAC address verification Enabled
Cisco IOS DHCP server binding database Enabled in Cisco IOS software, requires configuration.
Note The switch gets network addresses and configuration parameters
only from a device configured as a DHCP server.
DHCP snooping binding database agent Enabled in Cisco IOS software, requires configuration. This feature is
operational only when a destination is configured.