[39200] in North American Network Operators' Group
Re: Cable Modem [really responsible engineering]
daemon@ATHENA.MIT.EDU (Greg A. Woods)
Thu Jun 28 15:50:09 2001
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From: woods@weird.com (Greg A. Woods)
To: Fletcher E Kittredge <fkittred@gwi.net>
Cc: nanog@merit.edu (North America Network Operators Group Mailing List),
dhcp-server@isc.org
In-Reply-To: <200106281741.f5SHftt25000@smtp.gwi.net>
Reply-To: woods@weird.com (Greg A. Woods)
Message-Id: <20010628194842.6C272136@proven.weird.com>
Date: Thu, 28 Jun 2001 15:48:42 -0400 (EDT)
Errors-To: owner-nanog-outgoing@merit.edu
[ On Thursday, June 28, 2001 at 13:41:55 (-0400), Fletcher E Kittredge wrote: ]
> Subject: Re: Cable Modem [really responsible engineering]
>
> I haven't been able to figure your statement above out. I
> thought you were saying that given a client device MAC address, one
> could determine which cable modem MAC address was servicing that
> client MAC, even in the cases where the cable modem was just acting as
> a bridge.
Luckily not much of this thread has been polluting NANOG, so I'm not
100% sure what your goal is here, but I will point out that:
The client-IP addresses active on any CPE interface of any cable modem
compliant with the DOCS-CABLE-DEVICE-MIB (rfc2669) can easily be
discovered with SNMP. From there it's very simple to find the client
MAC in your dhcpd.leases file (though I don't know why the IP#s wouldn't
be sufficient for most needs). Note too that this same table should
also act as a filter to lock static addresses to a given modem if its
entries are assigned by the operator.
The only problem of course is that you've got to SNMP-scan all your
modems to find which customer's using a given IP# (I did that a couple
of times just this morning! ;-). There are no doubt ways to cache this
information, and maybe even refresh a cache intelligently. There may
even be a better, proprietary, way do do such searches in well
implemented head-end systems (doesn't seem to be in Terayon's though).
--
Greg A. Woods
+1 416 218-0098 VE3TCP <gwoods@acm.org> <woods@robohack.ca>
Planix, Inc. <woods@planix.com>; Secrets of the Weird <woods@weird.com>
