[ntp:questions] NTP on small 100% Linux LAN : reasonable access control policy ?

David Lord snews at lordynet.org
Sun Aug 1 15:11:22 UTC 2010

Niki Kovacs wrote:
> David Lord a écrit :
>> # servers previous to July 2010 had: restrict default noquery
>> # but now to reduce number of sites sending too frequent polls
>> restrict default kod nomodify notrap nopeer
>> # for local public lan segments
>> restrict a.b.c.d mask
>> restrict e.f.g.h mask
>> # for private lan segments
>> restrict s.t.u.v mask
>> restrict w.x.y.z mask
>> # for localhost
>> restrict
>> restrict -6 ::1 # only if ipv6 enabled
>> Servers have ntp traffic restricted by firewall rules and
>> in addition clients are behind NAT.
>> Client pcs (including laptops when used remote) are pointed to
>> my own servers. I think some have same restrict lines as
>> servers and others may have minimum:
>> restrict default noquery
>> restrict
>> restrict -6 ::1 # only if ipv6 enabled
> Oh wow. Thanks very much for that detailed explanation. I'll try it out 
> this afternoon.

Above server configuration is same as I use but it is open
to public access if you aren't firewalled or behind nat.
Your 'restrict default ignore' for server config could be a
safer option if you are open to the internet. I made use of
the firewall default deny for incoming connections up until
adding rules to allow ntp requests some weeks before I
joined the pool. I didn't notice any incoming requests other
than from my own remote connections during the few weeks
period before my ips were added to the pool dns rotation.


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