Use this command to insert the link selection (5) sub-option into the Relay Agent Information packet.
| IP-subnet | Specifies the IP subnet that should be included in the link selection sub-option. |
| vendor-id vendor-id | Specifies the vendor-id (DHCP option 60) to be included in the link selection sub-option. |
| mac mac-addr | Specifies the MAC address of the client hardware. This value can be a partial or full match, in hex format. For example, 01dead or 000203040506. |
None
Configuration command, Interface configuration.
The link selection sub-option is described in RFC 3527.
You can use this command to specify that the link selection sub-option should be included in the Relay Agent Information and to specify a different subnet from the primary IP address on the relay agent‘s interface. With this command, you can select a secondary IP address on the interface to be used to help in DHCP pool selection on the server. The subnet selection can be based on the DHCP client‘s vendor id (option 60) or the hardware MAC address.
When both the MAC address and vendor-id are configured for a specific subnet and the DHCP client can match on both values, the vendor-id link selection is used.
Within a VLAN, a maximum of 20 link selection subnet/vendor or MAC value combinations can be configured.
This example shows how you would use the link selection option to tell the DHCP server to assign leases from different sub-networks, depending on information received in the DHCP client request. For example, when the relay agent receives a DHCP client request from a host with MAC address 002654AF123B, the relay agent sets the DHCP relay agent information link selection option value to 10.180.2.0. If the MAC address were 00301E44AC12, the option value would be set to 10.180.3.0.
System(su)->configure System(su-config)->interface vlan.0.10 System(su-config-intf-vlan.0.10)->ip address 10.180.1.8 255.255.255.0 primary System(su-config-intf-vlan.0.10)->ip address 10.180.2.8 255.255.255.0 secondary System(su-config-intf-vlan.0.10)->ip address 10.180.3.8 255.255.255.0 secondary System(su-config-intf-vlan.0.10)->ip address 10.180.4.8 255.255.255.0 secondary System(su-config-intf-vlan.0.10)->ip directed-broadcast System(su-config-intf-vlan.0.10)->ip helper-address 11.5.255.255 global System(su-config-intf-vlan.0.10)->ip dhcp relay information option System(su-config-intf-vlan.0.10)->ip dhcp relay information option vpn System(su-config-intf-vlan.0.10)->ip dhcp relay information option remote-id Shrewsbury System(su-config-intf-vlan.0.10)->ip dhcp relay information option circuit-id engineering System(su-config-intf-vlan.0.10)->ip dhcp relay information option link-selection 10.180.2.0 mac 002654AF123B System(su-config-intf-vlan.0.10)->ip dhcp relay information option link-selection 10.180.2.0 vendor-id "MSFT 5.0" System(su-config-intf-vlan.0.10)->ip dhcp relay information option link-selection 10.180.3.0 mac 00301E44AC12 System(su-config-intf-vlan.0.10)->ip dhcp relay information option link-selection 10.180.4.0 mac 001CC504BC34 System(su-config-intf-vlan.0.10)->exit System(su-config)->
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