passing values to client: how big?

Jeffrey Hutzelman jhutz at
Tue Jan 13 22:18:09 UTC 2009

--On Tuesday, January 13, 2009 07:52:45 PM +0000 Simon Hobson 
<dhcp1 at> wrote:

> It's bound to be the case - if you make something optional, then there is
> bound to be an implementation that doesn't support it. So large packets
> are bound to be a problem somewhere. But I guess, when the spec was
> written, the packet size was considered to be quite adequate.

It's not just that.  The philosophy seems to be that the purpose of DHCP 
options is to provide configuration to the client that the client finds 
useful.  Thus, for example, a server normally only sends options that are 
in the PRL.  So, a client that needs large amounts of configuration can 
advertise support for a larger packet size, and one that doesn't need not 
do so, comfortable in the knowledge that the DHCP server is unlikely to 
overrun the packet size with options the client doesn't need and didn't 

Of course, that ignores the issues David described with relay agents and 
confusion over what packet size means.

-- Jeff

More information about the dhcp-users mailing list