Cisco IE4010 NTP issue

[grapevine]

Switch is unable to sync with NTP server

SW01#sh ntp packets
Ntp In packets : 0
Ntp Out packets : 222
Ntp bad version packets : 0
Ntp protocol error packets : 0

SW01#show ntp status
Clock is unsynchronized, stratum 16, no reference clock
nominal freq is 286.1023 Hz, actual freq is 286.0911 Hz, precision is 2**20
ntp uptime is 8355200 (1/100 of seconds), resolution is 3496
reference time is 00000000.00000000 (18:00:00.000 CST Thu Dec 31 1899)
clock offset is 0.0000 msec, root delay is 0.00 msec
root dispersion is 1253.18 msec, peer dispersion is 0.00 msec
loopfilter state is 'FSET' (Drift set from file), drift is 0.000000000 s/s
system poll interval is 8, never updated.

SW01#show ntp associations

address ref clock st when poll reach delay offset disp
~a.b.c.d .INIT. 16 - 1024 0 0.000 0.000 15937.
* sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured

SW01#show ntp information
Ntp Software Name : Cisco-ntpv4
Ntp Software Version : Cisco-ntpv4-1.0
Ntp Software Vendor : CISCO
Ntp System Type : Cisco IOS / APM86XXX

SW01#sh clock
18:46:26.079 CST Wed Mar 30 2011

SW01#show ntp config
ntp server a.b.c.d prefer

NTP server is a SEL-2488 Satellite-Synchronized Network Clock

On firewall I could see traffic NTP is being allowed. Please advise how to fix this

[Richard Burts]

We need some more information to be able to give you good advice. Is the SEL-2488 inside your network or is it external? If it is inside your network are there any log messages etc indicating attempts to learn time from your device?  Do you have IP connectivity from your device to the server?

[marce1000]

  - Could you try with another NTP server (preferably local on the intranet) as a sanity or reference test ?

  M.

[vishalbhandari]

Your switch is unable to sync with the NTP server because it is not receiving any NTP packets (Ntp In packets : 0). Here are a few things to check and try:

1. Firewall Rules – You mentioned that NTP traffic is allowed, but double-check if the firewall is allowing NTP responses (UDP port 123) both ways. Some firewalls allow outbound but block inbound responses.

2. Reachability to NTP Server – Ensure the switch can reach the NTP server by pinging it (ping a.b.c.d). If ICMP is blocked, try traceroute to verify network reachability.

3. Source Interface Configuration – If the switch has multiple interfaces, explicitly set the source interface for NTP:

   ntp server a.b.c.d prefer source VlanX

   Replace VlanX with the appropriate VLAN or interface that has reachability to the NTP server.

4. NTP Server Response – If possible, verify that the SEL-2488 is responding to NTP queries from the switch. You can use a Linux machine or another device to check (ntpq -p or ntpdate -q a.b.c.d).

5. Check for NTP Version Mismatch – Some NTP servers require a specific version. Try forcing NTPv4:

   ntp server a.b.c.d version 4

6. Debugging NTP – If the issue persists, enable debugging to check for errors:

   debug ntp packets debug ntp events

Try these steps and check if the switch starts receiving NTP packets.

[john1938]

We can ask AI ourselves and we're not looking for answers copied from AI tools.

[grapevine · Accepted solution]

Issue resolved, clock is now synchronised, SEL-2488 wasn't setup properly. Thanks all for your suggestion

[Richard Burts]

Thanks for the update. Glad that you were able to resolve the issue.