Configuration for option 121

Eric Helm helmwork at
Fri Jul 28 13:15:49 UTC 2006

Unfortunately, the 'option static-routes' is for code 33 which are
classful routes.
See the dhcp-options man page entry:

This option specifies a list  of  static  routes  that  the client
should  install  in  its  routing cache.  If multiple routes to the same
destination are specified, they are listed in descending order of
priority.The  routes  consist  of  a  list  of  IP address pairs.  The
first address is the destination address, and the second address  is the
router for the destination. The  default route ( is an illegal
destination for a static route.  To specify the  default  route,  use
the  routers option.Also, please note that this option is not intended
for classless IP routing - it does  not include a subnet mask.   Since
classless IP routing  is  now  the  most  widely deployed routing
standard,this option is virtually useless, and is not implemented by any
 of the popular DHCP clients, for example the Microsoft DHCP client.


Erestor Elensar wrote:
>> Hello,
>> I have a need to send multiple classless static routes via option 121 to
>> our DSL modems for NOC management purposes.
>> For instance:
>> to
>> to
>> to
>> Does anyone have a good example of how to setup the dhcpd.conf file for
>> this requirement?
>> Thanks,
>> Eric
> option static-routes
>     ;

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