IGMP (v3) older version querier timer on OSX

Brandon Applegate brandon at burn.net
Fri Oct 24 19:45:30 UTC 2014


First of all - if there is a better place to ask this, let me know.  I simply want to make sure the audience has the technical chops to try to answer the question.  So discussions.apple.com / macrumors are out.

I’m trying to figure out how OSX is behaving with regard to downgrading sent IGMP messages in the presence of “older” queriers.  I.e. if a query is heard from a router (querier) that is v2, start a timer and only speak (IGMP) in v2 until it expires.  From the definitions I’ve found of how to calculate this timer - that should be 260 seconds.  After this time, assuming we haven’t heard any further v2 queries - we can start speaking v3 again.  From my testing (using 10.9 Mavericks and the newest VLC) - this doesn’t happen.  From the network side, I’m using a Cisco 3750 with snooping and querier turned on (i.e. not a real mcast router).

If I turn these off and reboot, VLC causes IGMP v3 to be sent.  If I turn querier back on on my switch - OSX drops down to IGMP v2.  It just never seems to bounce back to v3.  I think I waited ~ 10 minutes on my last test, and it was still v2.

Thanks - and sorry this isn’t about systemd (although I am reading the thread and think it’s a great topic).

--
Brandon Applegate - CCIE 10273
PGP Key fingerprint:
830B 4802 1DD4 F4F9 63FE  B966 C0A7 189E 9EC0 3A74
"SH1-0151.  This is the serial number, of our orbital gun."

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