When I run the ip_multicast (and ip_multicast_select) regression tests for boost 1.55 on my Mac, they fail with these errors: ip/multicast.cpp:165: error in "ip_multicast_runtime::test": 49, Can't assign requested address ip/multicast.cpp:181: error in "ip_multicast_runtime::test": 49, Can't assign requested address I’m new to IPv6, but it looks like the regression test is making sure that IPv6 is available (multicast.cpp lines 128-132), and then it’s trying to join a IPv6 multicast group (lines 163-165) and leave it (lines 179-181), and failing both times. I’m not sure how to check whether multicast is enabled for IPv6 on this machine (which I’ve seen online as a possible reason for this failure), but then it seems like the regression test is not so great if it can fail due to the environment of the host computer instead of an actual bug in the boost library. Are there other reasons why this test would fail? Is there a way I can check whether multicast over IPv6 is allowed on this machine? Is there a recommended way to disable one particular subtest like this one? A #ifdef kind of thing? Thanks, Chris