NTP over a local network

Question

I have one server: 192.168.0.40 and 4 clients: 192.168.0.61-192.168.0.64. The clients are Raspberry Pis and so have no real time clock. Therefore the time is always wrong.

I have followed instructions here to make ntp.conf files:

server:

restrict default nomodify notrap noquery
restrict 127.0.0.1 

# -- CLIENT NETWORK -------
restrict 192.168.0.0 mask 255.255.255.0 nomodify notrap

# --- OUR TIMESERVERS ----- 
server 0.pool.ntp.org iburst
server 1.pool.ntp.org iburst
server 2.pool.ntp.org iburst
server 127.127.1.0

# --- NTP MULTICASTCLIENT ---

# --- GENERAL CONFIGURATION ---

# Undisciplined Local Clock.
fudge   127.127.1.0 stratum 9

# Drift file.
driftfile /var/lib/ntp/drift
broadcastdelay  0.008

# Keys file.
keys /etc/ntp/keys

client:

restrict default nomodify notrap noquery
restrict 127.0.0.1 

# -- CLIENT NETWORK -------

# --- OUR TIMESERVERS ----- 
# 192.168.1.2 is the address for my timeserver,
# use the address of your own, instead:
server 192.168.0.40 iburst
server  127.127.1.0

# --- NTP MULTICASTCLIENT ---

# --- GENERAL CONFIGURATION ---

# Undisciplined Local Clock.
fudge   127.127.1.0 stratum 12

# Drift file.
driftfile /var/lib/ntp/drift
broadcastdelay  0.008

# Keys file.
keys /etc/ntp/keys

However, the time on the clients is still wrong (unchanged from before). When I try connecting specifically to the server, the client cannot find it. They are 100% on the same subnet and the IP addresses are right as I can ssh no problem.

The result of ntpq -c lpeer is:

localhost: timed out, nothing received
***Request timed out

Edit:

sudo ntpdate -u 192.168.0.40 :

12 Dec 07:45:09 ntpdate[12815]: no server suitable for synchronization found

Edit 2:

The clients are on a subnet on the ethernet, and the server is connected on wifi. The system works when wifi is disabled. Is there a way around this?

It doesn't look as if your NTP server is listening for 192.168.0.40 has an NTP service listening. Did you restart the service? — muru, Feb 09 '15 at 14:41
That seems to be the answer. I had definitely restarted it before, but I think it needs to be restarted when I change the network? Post this as an answer and I'll nark it - thanks — user2290362, Feb 09 '15 at 14:45
No - this is clearly the issue. Not really sure why it should interfere like that though — user2290362, Feb 09 '15 at 15:00
Sorry, that was wrong. I can ping from the server to the client with wifi on but with ethernet connected, I can't access wifi. With wifi on, I can't get time on the client. — user2290362, Feb 09 '15 at 15:02

score 1 · Accepted Answer · answered Feb 09 '15 at 14:50

NTP probably needs to be restarted if you change networking settings (SSH does as well, for example). You can test if NTP is up and listening by using netstat on the server and ntpdate on the client

On the server:

$ sudo netstat -unlp | grep ntp
udp        0      0 192.168.122.1:123       0.0.0.0:*                 2786/ntpd          
udp        0      0 127.0.0.1:123           0.0.0.0:*                 2786/ntpd       
udp        0      0 0.0.0.0:123             0.0.0.0:*                 2786/ntpd       
udp6       0      0 fe80::4e72:b9ff:fe4:123 :::*                      2786/ntpd       
udp6       0      0 ::1:123                 :::*                      2786/ntpd       
udp6       0      0 :::123                  :::*                      2786/ntpd

On the client:

sudo ntpdate <server-ip/hostname>

@user2290362 Cron, perhaps?. Though I still think your routes are not properly configured and that you should look into fixing them. — muru, Feb 09 '15 at 15:05

NTP over a local network

1 Answers1