topic Re: Reg port number 123 NTP in Operating System - HP-UX

Reg port number 123 NTP

zxcv — Mon, 12 Dec 2011 10:29:06 GMT

Hi ,

We have a nexus switch 10.1.5.6 which is configured as ntp server.

when we are running from a client telnet 10.1.5.6 123 we are getting

telnet: connect: A remote host refused an attempted connect operation

Is it because of 123 being udp port ?

but my /etc/services show that its tcp port too .

Re: Reg port number 123 NTP

rariasn — Mon, 12 Dec 2011 12:19:45 GMT

HI:

You can use xntpdc command to test connection to ntp server.

xntpdc is used to query the xntpd daemon about its current state and to request changes in that state. The program may be run either in interactive mode or controlled mode using command line arguments.
Extensive state and statistics information is available through the xntpdc interface. In addition, nearly all the configuration options which can be specified at start up using xntpd's configuration file may also be specified at run time using xntpdc. If one or more request options is included on the command line when xntpdc is executed, each of the requests will be sent to the NTP servers running on each of the hosts given as command line arguments, or on localhost by default. If no request options are given, xntpdc will attempt to
read commands from the standard input and execute these on the NTP server running on the first host given on the command line, again defaulting to localhost when no other host is specified. xntpdc will
prompt for commands if the standard input is a terminal device.

man xntpdc

rgs,

Re: Reg port number 123 NTP

Patrick Wallek — Mon, 12 Dec 2011 14:27:07 GMT

NTP works only on the UDP port. So trying to telnet to port 123 will not work as telnet works over TCP.

Any port can be either TCP or UDP but /etc/services is purely for documentation purposes. Just because it is in /etc/services does not mean it is usable. The only way a port is available for use is if there is a program that opens it and listens for connections.