Microsoft Disable Netbios Option

[Meike Stone]

Hello dear list,

I try to configure "Microsoft Disable Netbios Option".
If I use:
option space MSFT;
option MSFT.nbt  code 1 = unsigned integer 32;
option MSFT.nbt 2;

nothing happens. The client has a acitvated the parameter "Netbios
over TCP/IP" (seen with ipconfig) after getting the IP via DHCP. But
the client sends in the discover in the "parameter request list"
(option 55) the options 43, but the server doesn't sends the option 43
back. (sniffed with wireshark)

If I remove the config from above and configure:

option vendor-encapsulated-options 01:04:00:00:00:02;

the client get's the option 43 from the server and the parameter
"Netbios over TCP/IP" (seen with ipconfig) is disabled as expected.

Why is one configration working and the other not?

(all configurations are done in the global section, I use ISC server
version 4.3.3 on SLES12SP3)

Thanks Meike
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[Anderson, Charles R]

You need to set the vendor-option-space.  You see, option 43 is "shared" among many different vendors and each vendor can have a different format for sub-options inside option 43.

For example, to set up the option space for APC vendor option codes, use this:

class "APC" {
  match if option vendor-class-identifier = "APC";
  option APC.cookie "1APC";
  option server.vendor-option-space APC;
}

and for Microsoft, this should work:

option space MSFT;
option MSFT.disable-netbios code 1 = unsigned integer 8;
option MSFT.release-on-shutdown code 2 = unsigned integer 32;
option MSFT.default-router-ttl code 3 = unsigned integer 32;

class "Microsoft Windows" {
  match if option vendor-class-identifier = "MSFT";
  option server.vendor-option-space MSFT;
}
class "Microsoft Windows 2000" {
  match if option vendor-class-identifier = "MSFT 5.0";
  option server.vendor-option-space MSFT;
}
class "Microsoft Windows 98/Me" {
  match if option vendor-class-identifier = "MSFT 98";
}


On Wed, Oct 10, 2018 at 04:09:00PM +0200, Meike Stone wrote:

> Hello dear list,
>
> I try to configure "Microsoft Disable Netbios Option".
> If I use:
> option space MSFT;
> option MSFT.nbt  code 1 = unsigned integer 32;
> option MSFT.nbt 2;
>
> nothing happens. The client has a acitvated the parameter "Netbios
> over TCP/IP" (seen with ipconfig) after getting the IP via DHCP. But
> the client sends in the discover in the "parameter request list"
> (option 55) the options 43, but the server doesn't sends the option 43
> back. (sniffed with wireshark)
>
> If I remove the config from above and configure:
>
> option vendor-encapsulated-options 01:04:00:00:00:02;
>
> the client get's the option 43 from the server and the parameter
> "Netbios over TCP/IP" (seen with ipconfig) is disabled as expected.
>
> Why is one configration working and the other not?
>
> (all configurations are done in the global section, I use ISC server
> version 4.3.3 on SLES12SP3)

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[Meike Stone]

Hello Charles,

Am Mi., 10. Okt. 2018 um 17:27 Uhr schrieb Anderson, Charles R <[hidden email]>:

>
> You need to set the vendor-option-space.  You see, option 43 is "shared" among many different vendors and each vendor can have a different format for sub-options inside option 43.
>
> For example, to set up the option space for APC vendor option codes, use this:
>
> class "APC" {
>   match if option vendor-class-identifier = "APC";
>   option APC.cookie "1APC";
>   option server.vendor-option-space APC;
> }
>
> and for Microsoft, this should work:
>
> option space MSFT;
> option MSFT.disable-netbios code 1 = unsigned integer 8;
> option MSFT.release-on-shutdown code 2 = unsigned integer 32;
> option MSFT.default-router-ttl code 3 = unsigned integer 32;
>
> class "Microsoft Windows" {
>   match if option vendor-class-identifier = "MSFT";
>   option server.vendor-option-space MSFT;
> }
> class "Microsoft Windows 2000" {
>   match if option vendor-class-identifier = "MSFT 5.0";
>   option server.vendor-option-space MSFT;
> }
> class "Microsoft Windows 98/Me" {
>   match if option vendor-class-identifier = "MSFT 98";
> }

option server.vendor-option-space MSFT;

That was the missing link ... I've looked (man dhcp* ) for such kind
of option, but noting found.
*Where is this "option" documented?*

I tried too:

option space MSFT;
option MSFT.disable-netbios code 1 = unsigned integer 8;

class "Microsoft Windows" {
    match if option vendor-class-identifier = "MSFT";
    MSFT.disable-netbios 2;
 }

Many thanks, now it works :-D

Meike

>
>
> On Wed, Oct 10, 2018 at 04:09:00PM +0200, Meike Stone wrote:
> > Hello dear list,
> >
> > I try to configure "Microsoft Disable Netbios Option".
> > If I use:
> > option space MSFT;
> > option MSFT.nbt  code 1 = unsigned integer 32;
> > option MSFT.nbt 2;
> >
> > nothing happens. The client has a acitvated the parameter "Netbios
> > over TCP/IP" (seen with ipconfig) after getting the IP via DHCP. But
> > the client sends in the discover in the "parameter request list"
> > (option 55) the options 43, but the server doesn't sends the option 43
> > back. (sniffed with wireshark)
> >
> > If I remove the config from above and configure:
> >
> > option vendor-encapsulated-options 01:04:00:00:00:02;
> >
> > the client get's the option 43 from the server and the parameter
> > "Netbios over TCP/IP" (seen with ipconfig) is disabled as expected.
> >
> > Why is one configration working and the other not?
> >
> > (all configurations are done in the global section, I use ISC server
> > version 4.3.3 on SLES12SP3)

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