ntp_response no contact with server or response time exceeded

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)
• CA Unified Infrastructure Management On-Premise (Nimsoft / UIM)
• CA Unified Infrastructure Management SaaS (Nimsoft / UIM)

Issue/Introduction

What is the significance of these ntp_response probe configuration parameters and what do they mean/indicate?

Environment

• DX UIM 23.4 CU3

Cause

• Guidance

Resolution

1. Response time exceeds: Enables the probe to send an alarm message when the maximum allowed response time is exceeded. Default: 100 ms

The default ms seems a bit low to me...I would increase it to 1000

2. No contact with server: Sends an alarm message when the probe is unable to connect to the server.

NTP server type: specifies whether the server type is SNTP (only a simple time-fetch is done) or NTP (an attempt is made to get server status information).
(applicable for NTP server only) NTP Version: specifies the version of the NTP server.

The NTP versions supported by the probe are NTPv2, NTPv3, and NTPv4.
Default: NTPv2

Server not running: The NTP server daemon might not be running or is not operational.

Server unreachable or not synchronized: The NTP server itself might be unreachable from the client's network, or it might not be synchronized to a reliable time source.

Server configuration errors: The NTP server configuration might be incorrect, preventing it from accepting requests from the client.

Server restricting access: The NTP server might have access control lists (ACLs) or other restrictions configured to prevent access from specific IP addresses or subnets. 

Other potential causes of no contact with an SNTP server

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1. Firewall Configuration:

UDP Port 123: SNTP (Simple Network Time Protocol) and NTP (Network Time Protocol) utilize User Datagram Protocol (UDP) packets on port 123 for communication. Ensure your firewall is configured to allow these packets to pass in BOTH directions (inbound and outbound).

NAT and ISP Blocking: Some Internet Service Providers (ISPs) may block outbound NTP traffic, especially if it appears to originate from port 123 (symmetric mode), according to a Super User discussion. If your Windows Time Service is configured to send packets from port 123 and responses come back to the same port, a stateless firewall might block them, according to the same discussion.

Router NAT: In some cases, your router's Network Address Translation (NAT) might rewrite UDP source ports, potentially hiding the issue. 

2. NTP/SNTP Server Issues:

Incorrect Server Address: Double-check the configured SNTP server IP address or hostname.

Server Unavailability: The specified SNTP server might be down or not responding. Try connecting to an alternative public SNTP server, such as pool.ntp.org.

Server Synchronization Issues: If the SNTP server you're using is configured to serve time only after it's synchronized, and it hasn't successfully synchronized with an upstream source, it won't be able to respond to client polls! 

3. Client Configuration Issues:

Time Differences: If the time difference between your client device and the SNTP server is significant, it might take longer for the client to synchronize.

NTP vs. SNTP: If you have both NTP and SNTP configured on the same device, the NTP process might interfere with SNTP's ability to synchronize.

Running NTP Service: On Linux systems, an active ntpd service might prevent other applications or the GUI from contacting external public NTP services. 

4. DNS Resolution:

DNS Issues: If you're using a hostname for the SNTP server, ensure that DNS resolution is working as expected. 

5. Troubleshooting Steps:

Verify Client Configuration: Check your device's SNTP client configuration for the correct server address.

Test Connectivity to the server using ping and traceroute/tracert.

NTP Client Test: Use an NTP client tool or command (e.g., ntpdate -qu <server_address>) to test direct communication with the server.

Check NTP Server Logs: If you have access to the SNTP server logs, look for any errors related to connection attempts or synchronization issues.

Consider Alternative Servers: If the current server isn't working, try a different, known-working SNTP server.

Additional Information

• Loss of conact with the server can occur if the local host or remote NTP server ip address is not being updated in the /etc/ntp.conf file.

• Ensure the correct selection of the NTP service type (ntpd or chrony) is based on the NTP service running on the server.