From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Lamparter Subject: Re: GRE devices and MULTICAST flag. Date: Fri, 23 Sep 2011 23:16:25 +0200 Message-ID: <20110923211625.GA2409116@jupiter.n2.diac24.net> References: <4E7CE473.3000304@candelatech.com> <4E7CEF4D.6080309@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev To: Ben Greear Return-path: Received: from spaceboyz.net ([87.106.131.203]:41982 "EHLO spaceboyz.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752340Ab1IWVQa (ORCPT ); Fri, 23 Sep 2011 17:16:30 -0400 Content-Disposition: inline In-Reply-To: <4E7CEF4D.6080309@candelatech.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Sep 23, 2011 at 01:42:53PM -0700, Ben Greear wrote: > On 09/23/2011 12:56 PM, Ben Greear wrote: > > I was under the impression that GRE tunnels could support MULTICAST > > traffic, but the MULTICAST flag is not set. This is making the xorp > > router crap out because it checks the MULTICAST flag and will > > not start multicast on the interface if it's not set.... > > > > Is it supposed to be set? > > > > 7: gre0: mtu 1476 qdisc noqueue state UNKNOWN > > link/gre 0.0.0.0 brd 0.0.0.0 > > 8: netb: mtu 1476 qdisc noqueue state UNKNOWN > > link/gre 192.168.100.223 peer 192.168.100.138 > > inet 10.0.1.1/32 scope global netb > > Well, ifconfig netb multicast seems to add the flag, > so maybe all is as it should be. I distinctively remember that the MULTICAST flag is supposed to be an input to the kernel, not a feature-indication flag output. I'm quite unsure where I picked this up, but I remember using it in that way that xorp does and then finding out it's wrong. -David