[ntp:questions] NTP to multiple networks via one interface.

Charles Elliott elliott.ch at verizon.net
Fri Dec 13 11:31:22 UTC 2013

I don't know much about VMs and nothing about xenserver, so beware of free
advice.  Here are three suggestions off the top of my head.

1. Would it be possible to have NTPD broadcast on both networks, x.x.75.x
and x.x.75.x?

2. Under Windows it appears to be possible to bridge connections on a dual
homed host.  Can xenserver bridge the two networks 75 and 69?

3. In a book on Java and networking the author offered an example of a
"repeater" written in Java.  All the program did, as I recall, was listen on
one interface and retransmit some packets to another interface.  I tried it,
and it worked.  I could try to find that book again, if it would help.

-----Original Message-----
From: questions-bounces+elliott.ch=verizon.net at lists.ntp.org
[mailto:questions-bounces+elliott.ch=verizon.net at lists.ntp.org] On Behalf Of
sc0tt.v3rn0n at gmail.com
Sent: Thursday, December 12, 2013 11:09 PM
To: questions at lists.ntp.org
Subject: [ntp:questions] NTP to multiple networks via one interface.


We have a xenserver host.  We manage it via an interface on x.x.75.x which
is the only network that is actually plumbed in on the host.  It has other
interfaces but they are virtualised by xen and don't have IP's.

We have several VM's on this host on the same x.x.75.x network so we have
set the xenserver to broadcast ntp (it syncs from network switches) and the
VM's to be broadcast clients .  NTP is working ok in this scenario.

However we've added a new network to xenserver on x.x.69.x but VM's on this
network don't receive the NTP broadcast packets as they don't have an
interface on the x.x.75 network.

Is there any way to get the NTP packets to all VM's without dual homing
either the xenserver or the VM's.

Thanks in advance,


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