The DHCP functionality supports the DHCP vendor class identifier option (option 60). This support allows DHCP relay to compare option 60 strings in received DHCP client packets against strings that you configure on the router. You can use the DHCP relay option 60 feature when providing converged services in your network environment—option 60 support enables DHCP relay to direct client traffic to the specific DHCP server that provides the service that the client requires. Or, as another option, you can configure option 60 strings to direct traffic to the DHCP local server in the current virtual router.
For example, you might have an environment in which some DHCP clients require only Internet access, while other clients require IPTV service. The clients that need Internet access get their addresses assigned by the DHCP local server on the E-series router (in equal-access mode). Clients requiring IPTV must be relayed to a specific DHCP server that provides the service. To support both types of clients, you configure two option 60 strings on the DHCP relay. Now, when any DHCP client packets are received with option 60 strings configured, the strings are matched against all strings configured on the DHCP relay. If the client string matches the first string you configured, that client is directed to the DHCP local server and gains Internet access. Client traffic with an option 60 string that matches your second string is relayed to the DHCP server that provides the IPTV service. In addition, you can configure a default action, which DHCP relay performs when a client option 60 string does not match any strings you have configured—for example, you might specify that all clients with non-matching strings be dropped.
in reference to:
Using Option 60 Strings to Forward Client Traffic to Specific DHCP Servers (
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