[mythtv-users] Way out idea on watchingsame thinginmultiplerooms

[Frank Merrill]

On Thu, Jan 7, 2010 at 2:10 PM, Eric Sharkey <eric at lisaneric.org> wrote:
> On Thu, Jan 7, 2010 at 6:14 AM, Gareth Glaccum
> <gareth.glaccum at btopenworld.com> wrote:
>> Yes, the switch is not up to the job, in that multicast is not properly
>> handled, or it is not configured correctly.
>
> I think you're overstating it.
>
> There are hubs, switches, and routers.  Generally, hubs always
> transmit on all ports, switches direct packets based on ethernet
> hardware addresses (and multicast packets generally have a broadcast
> ethernet hardware address), and routers direct packets based on higher
> level logic.
>
> If you buy a switch and it acts like a switch (and doesn't do what a
> router does), then it's not the case the "multicast is not properly
> handled or it is not configured correctly".  It's a switch and it's
> doing what a switch does.  If you want/need a router you should get a
> router.
>

This might be true if multicast were only a layer 3 technology, but
it's not.  Multicast has both layer 3 and layer 2 components to it,
and the layer 2 part does require configuration to be correct on a
layer 2 only device for it to work properly.  A switch (actually a
bridge) might well be doing it's job by sending multicast to all ports
if the configuration is not correct (or not possible) to handle it,
but, then that need to have it configured correctly is the point if it
is to be used properly in a multicast environment.

So, if you buy a switch and it acts like a switch, and it can't be
configured to properly handle multicast, then you bought the wrong
hardware if multicast is needed.