19c2daa00SOllivier Robert<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 29c2daa00SOllivier Robert<html> 39c2daa00SOllivier Robert<head> 49c2daa00SOllivier Robert<meta http-equiv="content-type" content="text/html;charset=iso-8859-1"> 59c2daa00SOllivier Robert<meta name="generator" content="HTML Tidy, see www.w3.org"> 69c2daa00SOllivier Robert<title>Server Commands and Options</title> 79c2daa00SOllivier Robert<!-- Changed by: Harlan &, 31-Jan-2014 --> 89c2daa00SOllivier Robert<link href="scripts/style.css" type="text/css" rel="stylesheet"> 99c2daa00SOllivier Robert</head> 109c2daa00SOllivier Robert<body> 119c2daa00SOllivier Robert<h3>Server Commands and Options</h3> 129c2daa00SOllivier Robert<img src="pic/boom3a.gif" alt="gif" align="left"><a href="http://www.eecis.udel.edu/~mills/pictures.html">from <i>Pogo</i>, 139c2daa00SOllivier RobertWalt Kelly</a> 149c2daa00SOllivier Robert<p>The chicken is getting configuration advice.</p> 159c2daa00SOllivier Robert<p>Last update: 169c2daa00SOllivier Robert <!-- #BeginDate format:En2m -->13-Feb-2020 10:08<!-- #EndDate --> 179c2daa00SOllivier Robert UTC</p> 189c2daa00SOllivier Robert<br clear="left"> 199c2daa00SOllivier Robert<h4>Related Links</h4> 209c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/command.txt"></script> 219c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/confopt.txt"></script> 229c2daa00SOllivier Robert<h4>Table of Contents</h4> 239c2daa00SOllivier Robert<ul> 249c2daa00SOllivier Robert <li class="inline"><a href="#address">Server and Peer Addresses</a></li> 259c2daa00SOllivier Robert <li class="inline"><a href="#command">Server Commands</a></li> 269c2daa00SOllivier Robert <li class="inline"><a href="#option">Server Command Options</a></li> 279c2daa00SOllivier Robert</ul> 289c2daa00SOllivier Robert<hr> 299c2daa00SOllivier Robert<h4 id="address">Server and Peer Addresses</h4> 309c2daa00SOllivier Robert<p>Following is a description of the server configuration commands in NTPv4. There are two classes of commands, configuration commands that configure an association with a remote server, peer or reference clock, and auxiliary commands that specify environment variables that control various related operations. </p> 319c2daa00SOllivier Robert<p>The various modes described on the <a href="assoc.html">Association Management</a> page are determined by the command keyword and the DNS name or IP address. Addresses are classed by type as (s) a remote server or peer (IPv4 class A, B and C or IPv6), (b) the IPv4 broadcast address of a local interface, (m) a multicast address (IPv4 class D or IPv6), or (r) a reference clock address (127.127.x.x). For type m addresses the IANA has assigned the multicast group address IPv4 224.0.1.1 and IPv6 ff05::101 (site local) exclusively to NTP, but other nonconflicting addresses can be used. </p> 329c2daa00SOllivier Robert<p>If the Basic Socket Interface Extensions for IPv6 (RFC-2553) is detected, 339c2daa00SOllivier Robert support for the IPv6 address family is generated in addition to the default IPv4 address family. IPv6 addresses can be identified by the presence of colons ":" in the address field. IPv6 addresses can be used almost everywhere where IPv4 addresses can be used, with the exception of reference clock addresses, which are always IPv4. Note that in contexts where a host name is expected, a <tt>-4</tt> qualifier preceding the host name forces DNS resolution to the IPv4 namespace, while a <tt>-6</tt> qualifier forces DNS resolution to the IPv6 namespace.</p> 349c2daa00SOllivier Robert<h4 id="command">Server Commands</h4> 359c2daa00SOllivier Robert<p>Unless noted otherwise, further information about these commands is on the <a href="assoc.html">Association Management</a> page.</p><dl> 369c2daa00SOllivier Robert <dt id="server"><tt>server <i>address</i> [options ...]</tt></dt> 379c2daa00SOllivier Robert <dt><tt>peer <i>address</i> [options ...]</tt></dt> 389c2daa00SOllivier Robert <dt><tt>broadcast <i>address</i> [options ...]</tt></dt> 399c2daa00SOllivier Robert <dt><tt>manycastclient <i>address</i> [options ...]</tt></dt> 409c2daa00SOllivier Robert <dt><tt>pool <i>address</i> [options ...]</tt></dt> 419c2daa00SOllivier Robert <dt><tt>unpeer [<i>address</i> | <i>associd</i>]</tt></dt> 429c2daa00SOllivier Robert <dd>These commands specify the remote server name or address to be used and the mode in which to operate. The <i>address</i> can be either a DNS name or a IPv4 or IPv6 address in standard notation. In general, multiple commands of each type can be used for different server and peer addresses or multicast groups. 439c2daa00SOllivier Robert <dl> 449c2daa00SOllivier Robert <dt><tt>server</tt></dt> 459c2daa00SOllivier Robert <dd>For type s and r addresses (only), this command mobilizes a persistent client mode association with the specified remote server or local reference clock. If the <tt>preempt</tt> flag is specified, a preemptable client mode association is mobilized instead.</dd> 469c2daa00SOllivier Robert <dt id="peer"><tt>peer</tt></dt> 479c2daa00SOllivier Robert <dd>For type s addresses (only), this command mobilizes a persistent symmetric-active mode association with the specified remote peer.</dd> 489c2daa00SOllivier Robert <dt id="broadcast"><tt>broadcast</tt></dt> 499c2daa00SOllivier Robert <dd>For type b and m addressees (only), this command mobilizes a broadcast or multicast server mode association. Note that type b messages go only to the interface specified, but type m messages go to all interfaces.</dd> 509c2daa00SOllivier Robert <dt id="manycastclient"><tt>manycastclient</tt></dt> 519c2daa00SOllivier Robert <dd>For type m addresses (only), this command mobilizes a preemptable manycast client mode association for the multicast group address specified. In this mode the address must match the address specified on the <tt>manycastserver</tt> command of one or more designated manycast servers. Additional information about this command is on the <a href="discover.html#mcst">Automatic Server Discovery</a> page.</dd> 529c2daa00SOllivier Robert <dt id="pool"><tt>pool</tt></dt> 539c2daa00SOllivier Robert <dd>For type s addresses (only) this command mobilizes a preemptable pool client mode association for the DNS name specified. The DNS name must resolve to one or more IPv4 or IPv6 addresses. Additional information about this command is on the <a href="discover.html#pool">Automatic Server Discovery</a> page. The <a href="http://www.pool.ntp.org/">www.pool.ntp.org</a> page describes a compatible pool of public NTP servers.</dd> 549c2daa00SOllivier Robert <dt id="unpeer"><tt>unpeer</tt></dt> 559c2daa00SOllivier Robert <dd>This command removes a previously configured association. An address or association ID can be used to identify the association. Either an IP address or DNS name can be used. This command is most useful when supplied via <tt><a href="ntpq.html">ntpq</a></tt> runtime configuration commands <tt>:config</tt> and <tt>config-from-file</tt>.</dd> 569c2daa00SOllivier Robert </dl></dd> 579c2daa00SOllivier Robert</dl> 589c2daa00SOllivier Robert<h4 id="option">Server Command Options</h4> 599c2daa00SOllivier Robert<dl> 609c2daa00SOllivier Robert <dt><tt>autokey</tt></dt> 619c2daa00SOllivier Robert <dd>Send and receive packets authenticated by the Autokey scheme described 629c2daa00SOllivier Robert on the <a href="autokey.html">Autokey Public Key Authentication</a> page. This option is mutually exclusive with the <tt>key</tt> option.</dd> 639c2daa00SOllivier Robert <dt id="burst"><tt>burst</tt></dt> 649c2daa00SOllivier Robert <dd>When the server is reachable, send a burst of packets instead of the usual one. This option is valid only with the <tt>server</tt> command and type s addresses. It is a recommended option when the <tt>maxpoll</tt> option is greater than 10 (1024 s). Additional information about this option is on the <a href="poll.html">Poll Program</a> page.</dd> 659c2daa00SOllivier Robert <dt><tt>iburst</tt></dt> 669c2daa00SOllivier Robert <dd>When the server is unreachable, send a burst of packets instead of the usual one. This option is valid only with the <tt>server</tt> command and type <tt>s</tt> addresses. It is a recommended option with this command. Additional information about this option is on the <a href="poll.html">Poll Program</a> page.</dd> 679c2daa00SOllivier Robert <dt><tt>ident</tt> <em><tt>group</tt></em></dt> 689c2daa00SOllivier Robert <dd>Specify the group name for the association. See the <a href="autokey.html">Autokey Public-Key Authentication</a> page for further information.</dd> 699c2daa00SOllivier Robert <dt><tt>key</tt> <i><tt>key</tt></i></dt> 709c2daa00SOllivier Robert <dd>Send and receive packets authenticated by the symmetric key scheme 719c2daa00SOllivier Robert described in the <a href="authentic.html">Authentication Support</a> 729c2daa00SOllivier Robert page. The <i><tt>key</tt></i> specifies the key identifier with values 739c2daa00SOllivier Robert from 1 to 65535, inclusive. This option is mutually exclusive with 749c2daa00SOllivier Robert the <tt>autokey</tt> 759c2daa00SOllivier Robert option.</dd> 769c2daa00SOllivier Robert <dt><tt>minpoll <i>minpoll</i></tt></dt> 779c2daa00SOllivier Robert <dt><tt>maxpoll <i>maxpoll</i></tt></dt> 789c2daa00SOllivier Robert <dd>These options specify the minimum and maximum poll intervals for NTP messages, in seconds as a power of two. The maximum poll interval defaults to 10 (1024 s), but can be increased by the <tt>maxpoll</tt> option to an upper limit of 17 (36 hr). The minimum poll interval defaults to 6 (64 s), but can be decreased by the <tt>minpoll</tt> option to a lower limit of 3 (8 s). Additional information about this option is on the <a href="poll.html">Poll Program</a> page.</dd> 799c2daa00SOllivier Robert <dt><tt>mode <i>option</i></tt></dt> 809c2daa00SOllivier Robert <dd>Pass the <tt><i>option</i></tt> to a reference clock driver, where <tt><i>option</i></tt> is an integer in the range from 0 to 255, inclusive. This option is valid only with type r addresses.</dd> 819c2daa00SOllivier Robert <dt><tt>noselect</tt></dt> 829c2daa00SOllivier Robert <dd>Marks the server or peer to be ignored by the selection algorithm as unreachable, but visible to the monitoring program. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd> 839c2daa00SOllivier Robert <dt><tt>preempt</tt></dt> 849c2daa00SOllivier Robert <dd>Specifies the association as preemptable rather than the default persistent. This option is ignored with the <tt>broadcast</tt> command and is most useful with the <tt>manycastclient</tt> and <tt>pool</tt> commands.</dd> 859c2daa00SOllivier Robert <dt><tt>prefer</tt></dt> 869c2daa00SOllivier Robert <dd>Mark the server as preferred. All other things being equal, this host will be chosen for synchronization among a set of correctly operating hosts. See the <a href="prefer.html">Mitigation Rules and the <tt>prefer</tt> Keyword</a> page for further information. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd> 879c2daa00SOllivier Robert <dt><tt>true</tt></dt> 889c2daa00SOllivier Robert <dd>Mark the association to assume truechimer status; that is, always survive the selection and clustering algorithms. This option can be used with any association, but is most useful for reference clocks with large jitter on the serial port and precision pulse-per-second (PPS) signals. Caution: this option defeats the algorithms designed to cast out falsetickers and can allow these sources to set the system clock. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd> 89 <dt><tt>ttl <i>ttl</i></tt></dt> 90 <dd>This option specifies the time-to-live <i><tt>ttl</tt></i> for the <tt>broadcast</tt> command and the maximum <i><tt>ttl</tt></i> for the expanding ring search used by the <tt>manycastclient</tt> command. Selection of the proper value, which defaults to 127, is something of a black art and should be coordinated with the network administrator. This option is invalid with type r addresses.</dd> 91 <dt><tt>version <i>version</i></tt></dt> 92 <dd>Specifies the version number to be used for 93outgoing NTP packets. Versions 1-4 are the choices, with version 4 the default.</dd> 94 <dt><tt>xleave</tt></dt> 95 <dd>Operate in interleaved mode (symmetric and broadcast modes only). Further information is on the <a href="xleave.html">NTP Interleaved Modes</a> page.</dd> 96 <dt><tt>xmtnonce</tt></dt> 97 <dd>Allowed in the server and pool modes, this flag causes the 98 client to put a random number nonce in the transmit timestamp of 99 its outgoing packet. Since the server will reply copying the 100 incoming transmit timestamp to the outgoing origin timestamp, this 101 flag provides extra security for the loopback test, at the expense 102 of the server having no idea what time the client thinks it is.</dd> 103</dl> 104<h4 id="aux">Auxiliary Commands</h4> 105<dl> 106 <dt id="broadcastclient"><tt>broadcastclient</tt></dt> 107 <dd>Enable reception of broadcast server messages to any local interface (type b address). Ordinarily, upon receiving a broadcast message for the first time, the broadcast client measures the nominal server propagation delay using a brief client/server exchange, after which it continues in listen-only mode. If a nonzero value is specified in the <tt>broadcastdelay</tt> command, the value becomes the delay and the volley is not executed. Note: the <tt>novolley</tt> option has been deprecated for future enhancements. Note that, in order to avoid accidental or malicious disruption in this mode, both the server and client should operate using symmetric key or public key authentication as described in the <a href="authopt.html">Authentication Options</a> page. Note that the volley is required with public key authentication in order to run the Autokey protocol.</dd> 108 <dt id="manycastserver"><tt>manycastserver <i>address</i> [...]</tt></dt> 109 <dd>Enable reception of manycast client messages (type m) to the multicasts group address(es) (type m) specified. At least one address is required. Note that, in order to avoid accidental or malicious disruption, both the server and client should operate using symmetric key or public key authentication as described in the <a href="authopt.html">Authentication Options</a> page.</dd> 110 <dt id="multicastclient"><tt>multicastclient <i>address</i> [...]</tt></dt> 111 <dd>Enable reception of multicast server messages to the multicast group address(es) (type m) specified. Upon receiving a message for the first time, the multicast client measures the nominal server propagation delay using a brief client/server exchange with the server, then enters the broadcast client mode, in which it synchronizes to succeeding multicast messages. Note that, in order to avoid accidental or malicious disruption in this mode, both the server and client should operate using symmetric key or public key authentication as described in the <a href="authopt.html">Authentication Options</a> page.</dd> 112 <dt id="mdnstries"><tt>mdnstries</tt> <i>number</i></dt> 113 <dd>If we are participating in mDNS, after we have synched for the first time we attempt to register with the mDNS system. If that registration attempt fails, we try again at one minute intervals for up to <tt>mdnstries</tt> times. After all, <tt>ntpd</tt> may be starting before mDNS. The default value for <tt>mdnstries</tt> is 5.</dd> 114</dl> 115<hr> 116<script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> 117</body> 118</html> 119
