[prev in list] [next in list] [prev in thread] [next in thread] 

List:       dhcp-users
Subject:    Re: need help understanding class matching
From:       jeffrey j donovan <donovan () beth ! k12 ! pa ! us>
Date:       2011-08-31 0:36:39
Message-ID: 750BBA39-8B12-41B0-A901-3DD07FC92EFD () beth ! k12 ! pa ! us
[Download RAW message or body]


On Aug 30, 2011, at 12:09 PM, Simon Hobson wrote:

> jeffrey j donovan wrote:
> 
> > > Really ?
> > > The hardware field (for an ethernet network) will contain a 1 (0x01) followed \
> > > by the 6 bytes of MAC address - it does not contain an ascii representation of \
> > > those bytes. To fetch the OUI of the MAC address you do need to get bytes 1 to \
> > > 3 of the hardware and compare with a 3 byte string.
> > 
> > okay not really, the syntax works but the clients are not matching.
> 
> That's what I thought
> 
> > i did see where someone did a conversion prior to the substring line. but I did \
> > not understand it; binary-to-ascii (16, 8, "", substring (hardware, 6, 1))),2) );
> > 
> > 
> > im thinking this might work
> > 
> > ahhh,..
> > i found this
> > http://blather.michaelwlucas.com/archives/962
> > 
> > class "sip-phone" {
> > match if (binary-to-ascii (16,8,":",substring(hardware, 0, 4)) = "1:0:3:e3")
> > or (binary-to-ascii (16,8,":",substring(hardware, 0, 4)) = "1:0:3:6b")
> > or (binary-to-ascii (16,8,":",substring(hardware, 0, 4)) = "1:0:7:eb");
> > log (info, (binary-to-ascii (16,8,":",substring(hardware, 0, 4))));
> > }
> > 
> > makes sense when I see it.
> 
> You do **NOT** have to do this. You can if you wish, but it is not necessary.
> 
> binary-to-ascii does what it says, and with the options specified will convert the \
> binary hardware address to a string representation. Then you can match against a \
> string. 
> However, you can save some typing, and processing time*, by just specifying the \
>                 match strings as the binary string you want to match against.
> * When a packet comes in, you have to do the binary to ascii conversion, for each \
> packet and for each time it's used in a class match. 
> so you can do :
> binary-to-ascii (16,8,":",substring(hardware, 1, 3)) = "0:11:ba3"
> or you can so :
> substring(hardware, 1, 3) = "\x00\x11\xba"
> 
> and I think (someone correct me if I'm wrong) you can write that latter one as \
> (note the lack of quotes) : substring(hardware, 1, 3) = 00:11:ba
> 

Thanks for your clarification , it really helps me understand my options.
This code is working for me.  I was getting confused on delimiters and basic \
counting. The machines are now matching. class "machines" {
		match if substring (hardware, 1,3) = 00:11:af
 		 or substring (hardware, 1,3) = 00:25:bc
		 or substring (hardware, 1,3) = 00:26:4a
		 or substring (hardware, 1,3) = 04:0c:ce
		 or substring (hardware, 1,3) = 04:1e:64
		 or substring (hardware, 1,3) = e8:06:88
		 or substring (hardware, 1,3) = f0:b4:79
		 or substring (hardware, 1,3) = f8:1e:df;
}

-j



_______________________________________________
dhcp-users mailing list
dhcp-users@lists.isc.org
https://lists.isc.org/mailman/listinfo/dhcp-users


[prev in list] [next in list] [prev in thread] [next in thread]