Reference implementation for RFC3442 (classless static route option) ?

Christoph Weber-Fahr cwf-ml at
Mon Feb 4 19:21:57 UTC 2008

[resend; the first instance should have bounced]


We are currently looking into the issue of supplying dhcp
clients with static routes via ISC dhcpd. This would
require option 121, as defined in RFC3442 (classless
static route option).

Apparently ISC-DHCPD doesn't support option 121 natively.

I've found a number of (diverging) recipes on the net to
get this working, the most common of which works along
these lines:

option classless-routes code 121 = array of uint8;

option classless-routes 32, 1,1,1,1, 5,5,5,1,
			24, 2,2,2,   5,5,5,1,
			24, 3,3,3,   5,5,5,1;

to implement to to to

(This example from a post by David W. Hankins to this list)

Now my question is - before we start to debate the 3442 support
with various vendors, is there a reference implementation
(either client or server) we could actually test this against?

And, of course - is the abovementioned example the correct way
to implement option 121 ?

And, while we are at it - is anybody able to give an educated
guess if and when ISC dhcpd will support option 121 natively ?

Any advice is gratefully appreciated ...


Christoph Weber-Fahr

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