Linksys + Juniper = Considered Harmful

David W. Hankins David_Hankins at isc.org
Mon Mar 23 18:00:47 UTC 2009


On Mon, Mar 23, 2009 at 06:34:21PM +0100, sthaug at nethelp.no wrote:
> It has considerably more functionality. But it's also newer, so I'm
> not too surprised that there are bugs to be found.

Unfortunately you can't see any of this new functionality on the wire.
:p

> I can partially reproduce this. Using a FreeBSD 7.0 box with an ISC
> client, Discover and Request are sent with the BROADCAST cleared.  My
> Juniper router, running JunOS 9.2R3.5 with the 'extended DHCP relay'
> functionality, sends the Offer to IP 255.255.255.255/Ethernet broadcast,
> but the ACK is sent unicast to the requested address.

That's weird.  Ours was definitely bradcasting both the OFFER and the
ACK.  I wonder if you trapped a unicast renewing-state DHCPREQUEST
rather than a braodcast requesting-state DHCPREQUEST?

> I would rather say that the moral is to get this problem reported to
> Juniper and fixed.

It's not really a bug in Juniper's software; the IP ttl behaviour in
the linksys is pretty bogus.

It's just in general - when Vista set the broadcast bit rather than
using Unicast like all the previous versions of Windows, people's
networks felt the pinch.  I don't understand why vendors have to keep
reinventing this.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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