Why NTP servers are rejected in RHEL?

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux (RHEL)

Issue

  • There are time synchronization issues in the server.
  • NTP client daemon rejects time sources:
ind assID status  conf reach auth condition  last_event cnt
===========================================================
  1 14233  9624   yes   yes  none  sys.peer   reachable  2
  2 14234  9024   yes   yes  none    reject   reachable  2
  3 14235  9024   yes   yes  none    reject   reachable  2
  4 14236  9024   yes   yes  none    reject   reachable  2
  • Flash values are flash=400 and flash=800.

Resolution

  • The NTP servers configured are not the best candidates.
  • Choose more reliable sources to avoid these issues.

Root Cause

Flash values are:

flash=400 peer_dist
	distance threshold exceeded

flash=800 peer_loop
	peer synchronization loop

"distance threshold exceeded" means ntpd thinks the server is too far away to be reliable.
"peer synchronization loop" occurs if the remote peer is synchronized to the local peer or the remote peer is synchronized to the current system peer.

Diagnostic Steps

  1. Run ntpq -p and check tally codes.
  2. Check flash codes for each assID.

From include/ntp.h:

/*
 * Peer errors
 */
#define TEST10		0x0200	/* peer bad synch or stratum */
#define	TEST11		0x0400	/* peer distance exceeded */
#define TEST12		0x0800	/* peer synchronization loop */
#define TEST13		0x1000	/* peer unreacable */
SBR
Product(s)
Components

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