Получение статических маршрутов от винды.

option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
option ms-classless-static-routes code 249 = array of unsigned integer 8;
request ...,static-routes,ms-classless-static-routes,rfc3442-classless-static-routes;

В /etc/dhcp/dhclient-exit-hooks будет доступно как $new_rfc3442_classless_static_routes
и $new_ms_classless_static_routes

Даже проще просто добавить

option rfc3442-classless-static-routes code 249 = array of unsigned integer 8;