Perform this task to enable support for the DHCP relay agent information option. For example, after receiving the option in the DHCP DISCOVER message, the relay agent will match and identify the relay class from the relay pool and then direct the DHCP DISCOVER message to the DHCP server associated with that identified relay class. The relay agent will match and identify the relay class from the relay pool and forward the DHCP message to the appropriate DHCP server identified by the The reply from the server is forwarded back to the client after removing option 82. The subnet selection suboption allows the separation of the subnet where the client resides from the IP address used to communicate with the relay agent. These two suboptions used together enable the deployment option vpn Displays all routes added by the Cisco IOS DHCP server and relay agent associated with an IP address. In typical DHCP processing, the gateway address specifies both the subnet on which a DHCP client resides and the IP address that the server can use to communicate with the relay agent. You can verify if they have been disabled by checking your configuration file.
You only need to configure helper addresses on the interface where the UDP broadcasts that you want to forward to the DHCP server are being received, and you only need the policy-action replace The unique identifier enables an ISP to identify a subscriber, to assign specific actions to that subscriber (for example, assignment of host IP address, subnet mask, and domain name system DNS), and to trigger accounting.
These relay pools can be configured with relay classes inside the pool that help determine the forwarding behavior.
The relay agent will set the giaddr to its own IP address so that DHCP messages are routable over the network. Forwards UPD broadcasts, including BOOTP and DHCP. Associates a class with a DHCP pool and enters DHCP pool class configuration mode. Configuring VPNs involves an adjustment to the usual DHCP host IP address designation. There is a DHCP server having IP address 192.168.2.2 and there is a router in middle which we wants as DHCP relay agent has an IP address 192.168.1.1 on interface fa0/0 and 192.168.2.1 on interface fa0/1. To access Cisco Feature Navigator, go to If the DHCP Relay Server ID Override and Link Selection Option 82 Suboptions feature and the DHCP Relay MPLS VPN Support feature are both configured, the DHCP Relay MPLS VPN Support feature takes precedence. You can use more than one helper address per interface. By default ip helper-address will forward broadcasts for these protocols: UDP 69 (TFTP), UDP 53 (DNS), UDP 37 (time service), UDP 137 (NetBIOS Name Server), UDP 138 (NetBIOS Datagram Server), UDP 67 and 68 (BOOTP client and server/DHCP), UDP 49 (TACACS), … networks where direct communication between the client and server is not The relay agent uses the server ID override suboption to force the DHCP server to use that value as the server ID in the DHCP message. possible or desired. The DHCP server sends the reply message to the IP address specified in the giaddr. Enable DHCP relay for eth1 and eth2: # set service dhcp-relay interface eth1 # set service dhcp-relay interface eth2 Set the IP address of the DHCP server: # set service dhcp-relay server 10.0.1.4 The router should discard DHCP packages already containing relay agent information to ensure that only requests from DHCP clients are forwarded: The DHCP relay agent intercepts the broadcast DHCP request packet and inserts a server ID override suboption and link selection suboption to its relay agent information option in the DHCP packet. See the This feature introduces the capability to manually configure the interface for the relay agent to use as the source IP address for messages relayed to the DHCP server.
You should configure the unique identifier for each subscriber. In some environments, a relay agent resides in a network element that also has access to one or more MPLS VPNs. If the DHCP Relay Server ID Override and Link Selection Option 82 Suboptions feature and the DHCP Relay MPLS VPN Support feature are both configured, the DHCP Relay MPLS VPN Support feature takes precedence.