netdev - Re: [PATCH 2/2] bridge: allow forwarding some link local frames

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Date:	Mon, 17 Oct 2011 16:07:15 -0700
From:	Ross Brattain <ross.b.brattain@...el.com>
To:	Ed Swierk <eswierk@...switch.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2] bridge: allow forwarding some link local frames

On Mon, 17 Oct 2011 14:09:34 -0700
Ed Swierk <eswierk@...switch.com> wrote:

> Interesting, I didn't realize LLDP could use any of those addresses.
> 
> I finally got a peek at the hot-off-the-presses IEEE 802.1Q-2011, and
> notice that 01-80-C2-00-00-0E is now assigned as "Individual LAN Scope
> group address, Nearest bridge group address" rather than dedicated to
> LLDP specifically.
> 

802.1AB-2009  Section 7.1 Destination address:

NOTE 8—The destination MAC address used by a given LLDP agent defines only the scope of transmission and the
intended recipient(s) of the LLDPDUs; it plays no part in protocol identification. In particular, the group MAC addresses
identified in Table 7-1 are not used exclusively by LLDP; other protocols that require to use a similar transmission scope
are free to use the same addresses.

> Since our application is generating the LLDP frames we could change it
> to use -00 or -03 and let the Linux bridge drop the -0E frames.
> 

If you control both end stations you could use the optional group MAC address support, or unicast LLDP.

802.1AB-2009  Section 7.1 Destination address:

In addition to the prescribed support for standard group MAC addresses shown in Table 7-1,
implementations of LLDP may support the following destination addresses for LLDPDUs:
d) Any group MAC address.
e) Any individual MAC address.
Support for the use of each of these destination addresses, for both transmission and reception of LLDPDUs,
is either mandatory, recommended, permitted, or not permitted, according to the type of system in which
LLDP is implemented, as shown in Table 7-2.

I have no idea if any LLDP agents support the optional group MAC addresses.

--
Ross
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