Administrator Guide

INTERFACE mode
ipv6 helper-address [vrf vrf-name] ipv6-address
Configuring DHCP relay source interface
The following section explains how to configure global and interface level DHCP relay source IPv4 or IPv6 configuration to
forward all the DHCP packets from the DHCP client to DHCP server through the configured source interface. This feature is
applicable only for L3 interface with relay configuration and L3 DHCP snooping enabled VLANs.
Global DHCP relay source IPv4 or IPv6 configuration
You can configure global DHCP relay source IPv4 or IPv6 configuration using the command {ip | ipv6} dhcp-relay
source-interface interface command in the CONFIGURATION mode. DHCP relay uses the IPv4 or IPv6 global source
address of the configured interface for relaying packets to the DHCP server. For example, if you configure DHCP relay source
interface as a loopback interface, the DHCP relay uses the configured loopback interface to forward the packets to the DHCP
server using the configured IPv4 or IPv6 address. The source interface can be a VLAN, LAG, physical and loopback interfaces.
● Specify the type of an interface and interface-number that should be used as a DHCP relay source interface.
CONFIGURATION mode
{ip | ipv6} dhcp relay source-interface interface
Following is the sample configuration to configure loopback interface with IPv4 and IPv6 address in CONFIGURATION MODE.
Dell(conf)# interface loopback 1
Dell(conf-if-lo-1)# ip vrf forwarding vrf1
Dell(conf-if-lo-1)# ip address 1.1.1.1/32
Dell(conf-if-lo-1)# ipv6 address 1::1/128
Dell(conf-if-lo-1)# no shutdown
To configure the loopback interface as IPv4 or IPv6 DHCP relay source interface, enter the following commands in the
CONFIGURATION MODE.
Dell(conf)# ip dhcp relay source-interface loopback 1
Dell(conf)# ipv6 dhcp relay source-interface loopback 1
When you configure the above commands in the CONFIGURATION MODE, it will configure the loopback interface as the DHCP
relay source interface for forwarding the DHCP packets from DHCP client to server. When this command is configured in the
CONFIGURATION mode level, it is applied globally. So, all the DHCP packets will be relayed or forwarded through the configured
L3 interface (loopback 1) using the IPv4 (1.1.1.1/32) and IPv6 addresses (1::1/128) of the loopback configuration.
Interface level DHCP relay source IPv4 or IPv6 configuration
You can configure interface specific DHCP relay source IPv4 or IPv6 configuration.
If the DHCP relay source interface is configured on the interface level, the DHCP relay forwards the packets from these
interfaces to the DHCP server using the interface. In case, the DHCP relay source interface is not configured in the interface
level (if configured), the DHCP relay chooses the configured global DHCP relay source interface for forwarding the packets.
NOTE:
The DHCP relay source IPv4 or IPv6 configuration at interface level takes precedence over the DHCP relay source IPv4 or
IPv6 configuration at the global level.
● Specify the type of an interface and interface-number that should be used as a DHCP relay source interface at the interface
level.
INTERFACE mode
{ip | ipv6} dhcp relay source-interface interface
Following are the steps to configure interface specific source IPv4 or IPv6 configuration for DHCP relay. The below example
shows when the DHCP relay uses the interface specific configuration and global source interface configuration depending on
the configuration.
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Dynamic Host Configuration Protocol (DHCP)