Connectivity Guide

OS10(config-vrf)#ip address dhcp
ip address dhcp
OS10(config)#interface 2/1/1
OS10(config-2/1/1)#ip vrf forwarding vrf-TEST
OS10(config-vrf-TEST)#ip address dhcp
.
DHCP relay agent
A DHCP relay agent relays DHCP messages to and from a remote DHCP server, even if the client and server are on dierent IP networks.
You can congure the IP address of the remote DHCP server.
You can congure a device either as a DHCP server or a DHCP relay agent — but not both.
If routes are not leaked between VRFs, the DHCP relay agent supports multi-virtual routing and forwarding (VRF) instances. The client-
facing and server-facing interfaces must be in the same VRF.
The DHCPv6 relay agent performs the same role as that of a DHCP relay agent, but in an IPv6 network. The DHCP relay agent forwards
the DHCPv4/DHCPv6 messages from the congured interface to the DHCPv6 server as a unicast message. The DHCP relay agent then
forwards the server’s response to the client.
When you congure DHCPv6 relay on an interface, you must:
• Congure an IPv6 address on the interface.
• Ensure that the DHCPv6 server is reachable.
Option 82 for security
DHCP, as dened by RFC 2131, provides no authentication or security mechanisms. To provide security, the DHCP relay agent supports
Option-82 with Circuit ID sub option, which is the printable name of the interface where the client request was received.
This option secures all DHCP trac that goes through a DHCP relay agent, and ensures that communication between the DHCP relay
agent and the DHCP server is not compromised.
The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the DHCP server. The DHCP server includes Option 82 back
in its response to the relay agent. The relay agent uses this information to forward a reply out the interface on which the request was
received rather than ooding it on the entire VLAN. However, the relay agent removes Option 82 from its DHCP responses before
forwarding the responses to the client.
NOTE
: Option 82 is supported, but not congurable.
Conguring a DHCP relay agent on an non-default VRF instance
To congure DHCP relay agent on an interface corresponding to a non-default VRF instance:
1 Enter the INTERFACE CONFIGURATION mode.
CONFIGURATION
OS10(config)#interface interface-name
interface 2/1/1
2 Congure the DHCP relay agent on the interface that is part of the non-default VRF instance. Specify the name of the non-default
VRF instance on which you want to run the relay agent.
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System management