[ntp:questions] Multicast question

Frank Kardel kardel at ntp.org
Sat Mar 1 10:18:43 UTC 2008

Danny Mayer wrote:
> John Vossler wrote:
>> Greetings,
>> I have a new system running Solaris 10 set up as an NTP server.  IT is 
>> synchronizing correctly but I cannot get it to multicast on any 
>> interface except the systems primary Ethernet interface, bge0.  I need 
>> it to multicast on interfaces bge1-bge3 and ce0 - ce7.
>> Client systems reside on the network segments on these other interfaces.
>> Anyone have any suggestions on getting the server to multicast on these 
>> other interfaces?
>> John
> Are you talking about outgoing packets to a multicast address? I think 
> that there may be some bugs in that area since the addresses are limited 
> and choosing an outgoing address becomes an issue and it will only send 
> it out on one address. I'm not sure if it's possible to set up a server 
> (at least not easily) to send via different interfaces.
It is. But on a multihomed server the server must have multicast routing
functionality. Either this is already provided in the kernel or you
need to run an mcast-routing daemon like mrouted, zebra or others.
The ntpd setup is not different on multihomed hosts. Just the multicast
routing must be working.

> To do this correctly you need to be able to set up a different multicast 
> address to use and associate it with a particular server address for 
> each interface.
NO - see above.

> The only way that I can think of to accomplish this is 
> to be able to specify a specific binding address in the config file. We 
> would have to add that as an optional parameter to the broadcast directive.
not needed.
> Danny


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