I can't use multicast on OpenBSD

[vale_shine]

Hi group I'm a newbie of OpenBSD systems and I have the following problem:
I'm interested in working with my openBSD virtual machine (under virtualbox) as a router but, when I use quagga, its routing deamons (ripd and ospfd) don't work.
it gives me the following output in /var/log/quagga/rip.log:
can't setsockopt ip_add_membership can't assign requested address
multicast join failed, interface em2 not running

but em2 is active and running!!

even if I try to start mrouted -d I receive the error:
can't enable multicast routing kernel: address already in use

I googled a little searching a solution for both problems and I found this link about the first error:
openbsd.7691.n7.nabble.com/quagga-0-99-20-1p0-multicast-broken-on-5-2-patch-included-td221123.html

but I don't have the skills to do what they suggest to.

and I couldn't find anything about the second output

do you have any suggestions ?? thanks and sorry for my english