Experience with answering option 252 with simple newline?

[Glenn Satchell]

On Tue, September 24, 2013 6:01 am, Jay Ford wrote:
> On Mon, 23 Sep 2013, John Wobus wrote:
>> We're considering replying to DHCPINFORMs
>> with option 252 with a newline to induce
>> clients to stop asking.
>> Anyone doing this on a large scale, i.e.
>> while trying to serve all sorts of clients?
>> In theory, something could break.
>> What I anticipate doing (globally):
>>
>> option msft-wpad code 252 = text;
>> if substring (option vendor-class-identifier, 0, 8) = "MSFT 5.0" {
>> 	option msft-wpad "\n";
>> 	}
>
> We do this on all of our normal DHCP servers to quell useless DHCPINFORM
> chatter by Microsoft devices, with good results:
>
>     # add option sequence for suppressing DHCPINFORM
>     #   Client browsers typically looking for wpad proxy sites
>     option wpad code 252 = text;
>     option wpad "\n\000";
>     class "MSFT" {
>      match if substring(option vendor-class-identifier, 0, 4) = "MSFT";
>     # They put 252 on the DHCPINFORM's, but not on the DHCPREQUEST's
>     # PRL.  So we over-ride the PRL to include 252 = null, which will
>     # send the option at DHCPDISCOVER/DHCPREQUEST time, and will also
>     # suppress the DHCPINFORMS!  They seem to cache it.
>      option dhcp-parameter-request-list = concat(option
> dhcp-parameter-request-list, fc);
>     }

Same here, although I actually set a URL in the wpad option.

Adding the option to the parameter request list, means it gets sent to the
client during the initial boot, and so the client doesn't need to do a
dhcpinform later to get that parameter.

regards,
-glenn