Devices not synching with the NTP server

[vitumbiko nkhwazi]

I have a router that i configured as an NTP server that all the other devices get NTP updates from, its a Cisco 4351 router running Version 15.5(2)S3, the NTP configuration is as below

ntp authentication-key 2 md5 107A514A3705180E30002E1D73086831 7
ntp authenticate
ntp trusted-key 2
ntp source Loopback0
ntp access-group serve ACL_NTP
ntp server 10.40.1.14 prefer

Client configuration is as below:

ntp authentication-key 2 md5 113D415625000109382E2F127F136E26 7
ntp authenticate
ntp trusted-key 2
ntp source Vlan1
ntp access-group peer ACL_NTP
ntp server 10.4.4.4 key 2 prefer

All the clients are unable to synchronize with the server, and am getting the following debug messages on the client:

[vitumbiko nkhwazi]

I did not upload the debug messages in the above message, see below:

*Jan 20 08:55:29.571: NTP Core(INFO): 10.4.4.4 E015 85 restart timeout
*Jan 20 08:55:29.572: NTP: ntpio_send_ipv4: dst 10.4.4.4, src 0.0.0.0, if_out Vlan1
*Jan 20 08:55:29.572: NTP message sent to 10.4.4.4, from interface 'Vlan1' (10.40.23.1).
*Jan 20 08:55:29.572: NTP Core(DEBUG): poll_update: clamp reached; limit 4943385 next 16110631

*Jan 20 08:55:29.582: NTP message received from 10.4.4.4 on interface 'Vlan1' (10.40.23.1).
*Jan 20 08:55:29.582: NTP Core(DEBUG): ntp_receive: message received
*Jan 20 08:55:29.582: NTP Core(DEBUG): ntp_receive: peer is 0x80FFFF4DAF54C8, next action is 1.
*Jan 20 08:55:29.582: NTP Core(DEBUG): poll_update: clamp reached; limit 4943385 next 16110631

[balaji.bandi]

as per the information i think some communication issue : Also check if you looking to be NTP master. configure (mentioned some document)

so i will start with basic config :

1. is the Client able to reach Server using that source interface ?

2. is the server able to reach same time to client using that interface ?

3. what is the content of ACL_NTP ( try to remove and test it)

post below output : From both the devices

#show ntp status

#show ntp associations

#show ntp packets

#show run interface vlan1 and loopbackX

some troubleshooting tips :

https://www.cisco.com/c/en/us/support/docs/ip/network-time-protocol-ntp/116161-trouble-ntp-00.html

EDIT : common issues with NTP :

https://blog.noblinkyblinky.com/2019/08/02/configuring-ntp-on-a-cisco-device/

https://community.cisco.com/t5/networking-knowledge-base/ntp-common-issues-and-troubleshooting/ta-p/3115895

[vitumbiko nkhwazi]

Thanks Balaji  for the reply.

fortunately, i have managed to figure out the reason it was not working, i was missing one command on the server "ntp master". soon as i configured this, all clients have managed to sync.

Regards.

[balaji.bandi]

glad to know - that is what my suggestion - Also check if you looking to be NTP master.