Is NTP version 1 or 2 or 3 supported in Red Hat Enterprise Linux?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 4
  • Red Hat Enterprise Linux 5
  • Red Hat Enterprise Linux 6
  • ntpd

Issue

  • What are NTP versions supported in Red Hat Enterprise Linux?
  • Is NTP version 1,2 and 3 is compatible with all versions of Red Hat Enterprise Linux?

Resolution

  • All current versions of Red Hat Enterprise Linux support NTP Version 4 by default but are compatible with NTP Version 1,2 and 3.

  • man ntpd says,

    DESCRIPTION
   The  ntpd  program  is  an  operating  system daemon that synchronises the system clock with remote NTP time
   servers or local reference clocks. It is a complete implementation of the Network Time Protocol  (NTP)  ver-
   sion  4,  but  also  retains  compatibility  with version 3, as defined by RFC-1305, and version 1 and 2, as
   defined by RFC-1059 and RFC-1119, respectively. The  program  can  operate  in  any  of  several  modes,  as
   described  on  the  Association Management page, and with both symmetric key and public key cryptography, as
   described on the Authentication Options page.

  • man ntp.conf says,

COMMAND OPTIONS 
      version version
               Specifies  the  version  number  to be used f or outgoing NTP packets. Versions 1-4 are the choices,
               with version 4 the default.
  • So use following setting in ntp.conf to get the same. Use version your ntp server supports.
[root@dhcp233-34 ]# grep server /etc/ntp.conf 
server 192.168.1.2 version 2   
[root@dhcp233-34 01422979]#
  • Restart ntp and same can be confirmed by tcpdump.

Diagnostic Steps

  • ntp.conf configuration
[root@dhcp233-34 ]# grep server /etc/ntp.conf 
server 192.168.1.2 version 2 
[root@dhcp233-34 ]#
  • tcpdump output,
[root@dhcp233-34 ~]# tcpdump -n -i eth0 host 192.168.1.2
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
17:05:35.916727 IP 192.168.1.1.ntp > 192.168.1.2.ntp: NTPv2, Client, length 48
17:05:36.218800 IP 192.168.1.2.ntp > 192.168.1.1.ntp: NTPv2, Server, length 48
  • Component
  • ntp

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