How to extract vendor specific information from Sub-Option 9 of Option 82

[Alan DeKok]

On Sep 5, 2025, at 4:31 AM, Ľudovít Mikula <ludovit.mikula at mikori.sk> wrote:
>  is it possible to automatically decode Vendor Specific Information from inocoming DHCP packet in freeradius 3.2.28?

 The DHCP xlat just uses the normal DHCP decoder, but there are limitations.

> In DHCP Discover Option 82 -> Sub-Option 9 I am receiving vendor specific information and I'd like to have it automatically decoded.
> 
> If I got the docs right, I need to create a dictionary and then the defined attributes should be accessible by %{dhcp_options:<Attribute-ref>}  (after enabling dhcp mod)

  The issue is that in v3, DHCP is already a "vendor" dictionary.  So it can't do vendor inside of vendor.

> I am a bit struggling with writing the dictionary tbh (I've checked also the suggested dictionary.alcatel.sr and dictionary.erx).
> 
> I am interested in two TLVs:
> 
> enterprise number: 0000061b (dec: 1563)
> 
>      03:
>        length: 0a (dec: 10)
>        data: 444d 5a2d 434f 532d 3032  ("DMZ-COS-02")
> 
>      01:
>        length: 0e (dec: 14)
>        data: 4554 492d 5250 442d 504f 5254 2d30 ("ETI-RPD-PORT-0")
> 
> 
> I was able to get the information with "unpack" from DHCP-Vendor-Specific-Information but am wondering whether this can be achieved by defining a custom dictionary and using dhcp_options ?

  Not in v3.

  And, of course, v4 supports this.  We're using it in production with DHCP vendor options.

  Alan DeKok.