4-6z If an S5500-EI Ethernet switch is enabled with DHCP snooping, the clients connected to it cannotdynamically obtain IP addresses through BOOTP.z You need to specify the ports connected to the valid DHCP servers as trusted to ensure that DHCPclients can obtain valid IP addresses. The trusted port and the port connected to the DHCP clientmust be in the same VLAN.z To enable DHCP snooping on an S5500-EI switch that belongs to an XRN fabric, do not configurethe ports connecting to the DHCP clients and DHCP server to belong to different units of the fabric;otherwise, the switch cannot record DHCP snooping entries although the clients can obtain IPaddresses.z You are not recommended to configure both the DHCP snooping and selective Q-in-Q function onthe switch, which may result in the DHCP snooping to function abnormally.Configuring DHCP Snooping to Support Option 82Enable DHCP snooping and specify trusted ports on the switch before configuring DHCP snooping tosupport Option 82.Complete the following tasks to configure the DHCP snooping to support Option 82:Task RemarksEnabling DHCP-snooping Option 82 support RequiredConfiguring a handling policy for DHCP packets with Option 82 OptionalConfiguring the storage format of Option 82 OptionalConfiguring the circuit ID sub-option OptionalConfiguring the remote ID sub-option OptionalConfiguring the padding format for Option 82 OptionalEnabling DHCP-snooping Option 82 supportFollow these steps to enable DHCP-snooping Option 82 support:To do… Use the command… RemarksEnter system view system-view —Enable DHCP-snooping Option82 supportdhcp-snooping informationenableRequiredDisabled by default.
