> These are link-local addresses ala rfc3927. That must be the issue.
> The kernel doesn't bind to the given interface. It doesn't return an
> error but rather selects some other random interface?!
>
> Sounds like a kernel bug, or maybe there is some sysctl (rp_filter?)
> that allows multicast on link-local interfaces.
169.254.0.0/16 should be a perfectly reasonable management domain, which
is what we are using it for in our product.
My understanding of RFC 3927 is that routers are not to forward link
local traffic, regardless of the TTL. A host shouldn't be banned from
sending multicast traffic to a link local interface.
PTP needs to "work" over a local 169.254.0.0/16 network. This isn't
unreasonable.
Please point me to the RFCs that say otherwise. If I'm off in the weeds,
I'd like to know the source.
I'm not aware of any systemctl option that controls multicast.
We are running the stock Ubuntu kernel. I'll have to look at the kernel
multicast binding code this week.
Thanks.
Bob Carter
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