Help with NTP on a new Cisco 3850 switch

Posted on 2014-10-27
Last Modified: 2014-11-04
Hello All,
Hello All,

We put in a new Cisco 3850 this last weekend.  The switch is working fine except for NTP.  The new switch is supposed to be the NTP server for the network.  However, other switches and servers are not syncing with the new switch, and I'm not seeing what the issue is.  The new switch is syncing with the atomic clock fine.  Below is the configuration for NTP on the new switch.

SW3850#show run | i ntp
ntp source Vlan2
ntp access-group peer 10
ntp access-group serve-only 20
ntp master
ntp server source Vlan2
ntp server prefer source Vlan2
ntp server source Vlan2
ntp server source Vlan2

Nick Dalmolin
Question by:ndalmolin_13
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Expert Comment

by:Craig Beck
ID: 40407922
Can you post ACL 10 and 20 too please?
LVL 12

Accepted Solution

Fidelius earned 500 total points
ID: 40407927

Remove command ntp master. By default, if this switch is configured with the external NTP server, it will act as NTP Master for the rest of devices in your network which point to it as NTP server.

Here is explanation of command:


LVL 45

Expert Comment

by:Craig Beck
ID: 40408484
Fidelius is right, but that wont 'stop' clients connecting to the switch as a ntp client.  It just forces the switch to give the time to clients from its own hardware clock.
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LVL 12

Expert Comment

ID: 40409356
I agree. But ntp master command sometimes makes trouble. As it is not needed in this case, it is better to remove it, before further troubleshoot
LVL 45

Expert Comment

by:Craig Beck
ID: 40409413
The only trouble I've ever had with ntp master is when you have more than one in your network.  This can cause stratum issues and loss of sync.  I do agree though, it's not required - I was just mentioning that it won't stop devices from syncing as clients.

Author Closing Comment

ID: 40421700
Thanks all for the help.  Apologies for not getting back to this sooner.  I was out of the office last week.
LVL 45

Expert Comment

by:Craig Beck
ID: 40421850
So did the chosen answer work?

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