[Cerowrt-devel] mdns reflector issues on ipv6/babel routing through nat.

Dave Taht dave.taht at gmail.com
Sun Mar 18 17:24:14 EDT 2012

On Sun, Mar 18, 2012 at 2:22 PM, Dave Taht <dave.taht at gmail.com> wrote:
> Once you get to a few routers, a few deep, (3 in series in this case,
> 9 overall), the avahi mdns proxy starts to malfunction over ipv6, and
> I ended up with a rather nasty broadcast storm.
> So I had to disable the ipv6 multicast of mdns in order to get my
> network back in this (excessively) complex network.
> use-ipv6=no in the /etc/avahi/avahi-daemon file
> Seems to work fine, two deep. Curiously, I did not observe a similar
> storm for ipv4...
> Now this is across like 5 different versions of cerowrt, but it would
> not surprise me that this is a  generic problem with avahi on ipv6,
> and/or a symptom of the brain-damaged-ness of mdns in the first place.
> use-ipv6=no
> I note that when you connect cero boxes together in a babel mesh
> configuration, site-local multicast is not a problem, because it
> doesn't work in the first place (by design). This can be construed as
> an advantage (no broadcast storm), or disadvantage (mdns and
> site-local multicast doesn't work across meshed links)

Actually  I was wrong. I'm STILL observing a broadcast storm, AND it
is taking place across the meshed links too.... aggggh.....

> Incidentally, I don't know if anyone would purposely inflict a network
> this complex on themselves:
> http://pastebin.com/LzeeiCXg
> but it does illustrate that a complex, automagically routed, fault
> tolerant ipv4 and ipv6 network IS feasible, so long as all internal
> addresses are unique.
> The biggest problem I run into is that 'failover-capable,
> fault-tolerant routing' introduces major headaches with firewall
> rules.
> Another thing the above paste illustrates that you can mix and match
> ipv4 nat with ipv6 fully meshed routing.
> The box I took that trace off has babel enabled on all interfaces, and
> has the following rule at the top of it's babeld.conf file
> out if ge00 ip deny
> (as do multiple other boxes in the lab on the external network)
> this prohibits announcing ipv4 routes across the natted ge00
> interface, but allows ipv6. In the caseof that paste, this particular
> router has NO internal wired connections at all, it just meshes
> internally for ipv4, and because ge00 is a higher quality (ethernet)
> interface, babel chooses it for the default for ipv6 for most routes.
> --
> Dave Täht
> SKYPE: davetaht
> US Tel: 1-239-829-5608
> http://www.bufferbloat.net

Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608

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