[ntp:questions] Multicast question

Frank Kardel kardel at ntp.org
Sat Mar 15 06:35:13 UTC 2008

Danny Mayer wrote:
> Jan Ceuleers wrote:
>> Martin Burnicki wrote:
>>> I'd expect that either the kernel routed multicast packets to all interfaces
>>> (isn't that what routers do with multicasts, contrarily to broadcasts?), or
>>> the application would send an individual packet on each interface.
>> Routers have to be told (by means of multicast protocols such as IGMP) 
>> which interfaces to replicate multicast packets onto.
> That assumes that there's a router involved. If it's just to the local 
> LAN then you may not have a router able to route to the other 
> interfaces. In this case it almost certainly have to be done on the 
> local server sending the packets.
> Danny
Well, when you install/enable multicast routing software on the local
machine this machine becomes a multicast router (kernel may have to
be compiled with the right flags on some systems). Thus the local
machine will be NTP server and multicast router.As I said you need
the multicast routing functionality in order to be able to find the
interfaces where you need to replicate to packets to.


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