The DHCPv4 option Classless Static Route allows a DHCP server to pass a list of static routes to a DHCP client, which then enters those routes into its routing table. The routes in this list are "Classless", i.e. a subnet mask or prefix length is transmitted for each route. According to RFC 3442, the option number 121 is used for this purpose.
On receiving this list, the DHCP client does not install a default route to the specified router, but only the list of the static routes in its routing table.
This feature is used, for example, by ISPs in scenarios where multiple virtual connections are separated by VLAN according to the individual service, e.g. with one VLAN each for Internet, VoIP and IPTV. In this case, the default route is used for the Internet connection (e.g. via PPPoE or DHCP), while the routes for IPTV are directed via a different VLAN as communicated by DHCP Classless Static Route Option.
By default, the LANCOM DHCPv4 client requests both the router option and the "Classless Static Routes" option. If the DHCP server sends a "Classless Static Routes" option, the client ignores any router option and only installs the list of routes. This behavior conforms with RFC 3442.
For a provider scenario with IPTV, you create a new DSL remote site with hold time 9999, layer DHCPOE and the corresponding VLAN according to provider specifications. Activate the switch Establish remote site even without route (keepalive without route) under . No entries are required in the routing table as the DHCP client provides the necessary routes by means of the "Classless Static Route" option.
The LANCOM DHCP server can also use a user-defined option to assign the "Classless Static Route" option to DHCP clients. Refer to section DHCP options for information on this.
