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10: <h3>Server Options</h3>
11: <img src="pic/boom3a.gif" alt="gif" align="left"><a href="http://www.eecis.udel.edu/~mills/pictures.html">from <i>Pogo</i>,
12: Walt Kelly</a>
13: <p>The chicken is getting configuration advice.</p>
14: <p>Last update:
15: <!-- #BeginDate format:En2m -->25-Nov-2009 4:46<!-- #EndDate -->
16: </p>
17: <br clear="left">
18: <h4>Related Links</h4>
19: <script type="text/javascript" language="javascript" src="scripts/command.txt"></script>
20: <script type="text/javascript" language="javascript" src="scripts/confopt.txt"></script>
21: <h4>Table of Contents</h4>
22: <ul>
23: <li class="inline"><a href="#cfg">Configuration Commands</a></li>
24: <li class="inline"><a href="#opt">Command Options</a></li>
25: <li class="inline"><a href="#aux">Auxilliary Commands</a></li>
26: <li class="inline"><a href="#bug">Bugs</a></li>
27: </ul>
28: <hr>
29: <p>Following is a description of the configuration commands in NTPv4. There are
30: two classes of commands, configuration commands that configure an association
31: with a remote server, peer or reference clock, and auxilliary commands that
32: specify environmental variables that control various related operations. </p>
33: <p>The various modes described on the <a href="assoc.html">Association Management</a> page
34: are determined by the command keyword and the DNS name or IP address. Addresses
35: are classed by type as (s) a remote server or peer (IPv4 class A, B and C),
36: (b) the IP broadcast address of a local interface, (m) a multicast address (IPv4
37: class D), or (r) a reference clock address (127.127.x.x). For type m addresses
38: the IANA has assigned the multicast group address IPv4 224.0.1.1 and IPv6 ff05::101
39: (site local) exclusively to NTP, but other nonconflicting addresses can be used. </p>
40: <p>If the Basic Socket Interface Extensions for IPv6 (RFC-2553) is detected,
41: support for the IPv6 address family is generated in addition to the default
42: IPv4 address family. IPv6 addresses can be identified by the presence of colons ":" in
43: the address field. IPv6 addresses can be used almost everywhere where IPv4 addresses
44: can be used, with the exception of reference clock addresses, which are always
45: IPv4. Note that in contexts where a host name is expected, a <tt>-4</tt> qualifier
46: preceding the host name forces DNS resolution to the IPv4 namespace, while a <tt>-6</tt> qualifier
47: forces DNS resolution to the IPv6 namespace.</p>
48: <h4 id="cfg">Configuration Commands</h4>
49: <dl>
50: <dt id="server"><tt>server <i>address</i> [options ...]</tt><br>
51: <tt>peer <i>address</i> [options ...]</tt><br>
52: <tt>broadcast <i>address</i> [options ...]</tt><br>
53: <tt>manycastclient <i>address</i> [options ...]</tt><br>
54: <tt>pool <i>address</i> [options ...]</tt><br>
55: <tt>unpeer [<i>address</i> | <i>associd</i>]</tt></dt>
56: <dd>These commands specify the time server name or address to be used and the
57: mode in which to operate. The <i>address</i> can be either a DNS name or a
58: IPv4 or IPv6 address in standard notation. In general, multiple commands of
59: each type can be used for different server and peer addresses or multicast
60: groups.
61: <dl>
62: <dt><tt>server</tt></dt>
63: <dd>For type s and r addresses (only), this command mobilizes a persistent
64: client mode association with the specified remote server or local reference
65: clock. If the <tt>preempt</tt> flag is specified, a preemptable client mode
66: association is mobilized instead.</dd>
67: <dt><tt>peer</tt></dt>
68: <dd>For type s addresses (only), this command mobilizes a persistent symmetric-active
69: mode association with the specified remote peer.</dd>
70: <dt><tt>broadcast</tt></dt>
71: <dd>For type b and m addressees (only), this command mobilizes a persistent
72: broadcast or multicast server mode association. Note that type
73: b messages go only to the interface specified, but type m messages go to
74: all interfaces.</dd>
75: <dt><tt>manycastclient</tt></dt>
76: <dd>For type m addresses (only), this command mobilizes a manycast client
77: mode association for the multicast group address specified. In this mode
78: the address must match the address specified on the <tt>manycastserver</tt> command
79: of one or more designated manycast servers.</dd>
80: <dt><tt>pool</tt></dt>
81: <dd>For type s messages (only) this command mobilizes a client mode association
82: for servers implementing the pool automatic server discovery scheme described
83: on the <a href="assoc.html">Association Management</a> page. The address
84: is a DNS name in the form <tt><i>area</i>.pool.ntp.org</tt>, where <tt><i>area</i></tt> is
85: a qualifier designating the server geographic area such as <tt>us</tt> or <tt>europe</tt>.</dd>
86: <dt><tt>unpeer</tt></dt>
87: <dd>This command removes a previously configured association. An address or association ID can
88: be used to identify the association. Either an IP address or DNS name can be used. This
89: command is most useful when supplied via <tt><a href="ntpq.html">ntpq</a></tt> runtime
90: configuration commands <tt>:config</tt> and <tt>config-from-file</tt>.</dd>
91: </dl></dd>
92: </dl>
93: <h4 id="opt">Command Options</h4>
94: <dl>
95: <dt><tt>autokey</tt></dt>
96: <dd>Send and receive packets authenticated by the Autokey scheme described
97: in the <a href="authopt.html">Authentication Options</a> page. This option
98: is mutually exclusive with the <tt>key</tt> option.</dd>
99: <dt><tt>burst</tt></dt>
100: <dd>When the server is reachable, send a burst of eight packets instead of the
101: usual one. The packet spacing is normally 2 s; however, the spacing between
102: the first and second packets can be changed with the <a href="miscopt.html"><tt>calldelay</tt></a> command
103: to allow additional time for a modem or ISDN call to complete. This option
104: is valid only with the <tt>server</tt> command and type s addressesa.
105: It is a recommended option when the <tt>maxpoll</tt> option is greater than
106: 10 (1024 s).</dd>
107: <dt><tt>iburst</tt></dt>
108: <dd>When the server is unreachable, send a burst of eight packets instead of
109: the usual one. The packet spacing is normally 2 s; however, the spacing between
110: the first and second packets can be changed with the <a href="miscopt.html"><tt>calldelay</tt></a> command
111: to allow additional time for a modem or ISDN call to complete. This option
112: is valid only with the <tt>server</tt> command and type s addresses. It is
113: a recommended option with this command.</dd>
114: <dt><tt>key</tt> <i><tt>key</tt></i></dt>
115: <dd>Send and receive packets authenticated by the symmetric key scheme described
116: in the <a href="authopt.html">Authentication Options</a> page.
117: The <i><tt>key</tt></i> specifies the key identifier with values from 1 to
118: 65534, inclusive. This option is mutually exclusive with the <tt>autokey</tt> option.</dd>
119: <dt><tt>minpoll <i>minpoll<br>
120: </i></tt><tt>maxpoll <i>maxpoll</i></tt></dt>
121: <dd>These options specify the minimum and maximum poll intervals for NTP messages,
122: in seconds as a power of two. The maximum poll interval defaults to 10
123: (1024 s), but can be increased by the <tt>maxpoll</tt> option to an upper limit
124: of 17 (36 h). The minimum poll interval defaults to 6 (64 s), but can
125: be decreased by the <tt>minpoll</tt> option to a lower limit of 3 (8 s).</dd>
126: <dt><tt>mode <i>option</i></tt></dt>
127: <dd>Pass the <tt><i>option</i></tt> to a reference clock driver, where <tt><i>option</i></tt> is
128: an integer in the range from 0 to 255, inclusive. This option is valid
129: only with type r addresses.</dd>
130: <dt><tt>noselect</tt></dt>
131: <dd>Marks the server or peer to be ignored by the selection algorithm but visible
132: to the monitoring program. This option is ignored with the <tt>broadcast</tt> command.</dd>
133: <dt><tt>preempt</tt></dt>
134: <dd>Specifies the association as preemptable rather than the default persistent.
135: This option is ignored with the <tt>broadcast</tt> command and is most useful
136: with the <tt>manycastclient</tt> and <tt>pool</tt> commands.</dd>
137: <dt><tt>prefer</tt></dt>
138: <dd>Mark the server as preferred. All other things being equal, this host will
139: be chosen for synchronization among a set of correctly operating hosts. See
140: the <a href="prefer.html">Mitigation Rules and the <tt>prefer</tt> Keyword</a> page
141: for further information. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd>
142: <dt><tt>true</tt></dt>
143: <dd>Mark the association to assume truechimer status; that is, always survive
144: the selection and clustering algorithms. This option can be used with any association,
145: but is most useful for reference clocks with large jitter on the serial port
146: and precision pulse-per-second (PPS) signals. Caution: this option defeats
147: the algorithms designed to cast out falsetickers and can allow these sources
148: to set the system clock. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd>
149: <dt><tt>ttl <i>ttl</i></tt></dt>
150: <dd>This option specifies the time-to-live <i><tt>ttl</tt></i> for the <tt>broadcast</tt> command
151: and the maximum <i><tt>ttl</tt></i> for the expanding ring search used by the <tt>manycastclient</tt> command.
152: 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>
153: <dt><tt>version <i>version</i></tt></dt>
154: <dd>Specifies the version number to be used f
155: or outgoing NTP packets. Versions
156: 1-4 are the choices, with version 4 the default.</dd>
157: <dt><tt>xleave</tt></dt>
158: <dd>Operate in interleaved mode (symmetric and broadcast modes only). (see <a href="xleave.html">NTP
159: Interleaved Modes</a>)</dd>
160: </dl>
161: <h4 id="aux">Auxilliary Commands</h4>
162: <dl>
163: <dt id="broadcastclient"><tt>broadcastclient</tt></dt>
164: <dd>Enable reception of broadcast server messages to any local interface (type
165: b address). Ordinarily, upon receiving a broadcast message for the first
166: time, the broadcast client measures the nominal server propagation delay using
167: a brief client/server exchange, after which it continues in listen-only mode.
168: If a nonzero value is specified in the <tt>broadcastdelay</tt> command, the
169: value becomes the delay and the volley is not executed. Note: the <tt>novolley</tt> option
170: has been deprecated for future enhancements. Note that, in order to avoid
171: accidental or malicious disruption in this mode, both the server and client
172: should operate using symmetric key or public key authentication as described
173: in the <a href="authopt.html">Authentication
174: Options</a> page. Note that the <tt>novolley</tt> keyword is incompatible with
175: public key authentication.</dd>
176: <dt id="manycastserver"><tt>manycastserver <i>address</i> [...]</tt></dt>
177: <dd>Enable reception of manycast client messages (type m)to the multicast group
178: address(es) (type m) specified. At least one address is required. Note that,
179: in order to avoid accidental or malicious disruption, both the server and client
180: should operate using symmetric key or public key authentication as described
181: in the <a href="authopt.html">Authentication Options</a> page.</dd>
182: <dt id="multicastclient"><tt>multicastclient <i>address</i> [...]</tt></dt>
183: <dd>Enable reception of multicast server messages to the multicast group address(es)
184: (type m) specified. Upon receiving a message for the first time, the multicast
185: client measures the nominal server propagation delay using a brief client/server
186: exchange with the server, then enters the broadcast client mode, in which it
187: synchronizes to succeeding multicast messages. Note that, in order to avoid
188: accidental or malicious disruption in this mode, both the server and client
189: should operate using symmetric key or public key authentication as described
190: in the <a href="authopt.html">Authentication Options</a> page.</dd>
191: </dl>
192: <h4 id="bug">Bugs</h4>
193: <p>The syntax checking is not picky; some combinations of ridiculous and even
194: hilarious options and modes may not be detected.</p>
195: <hr>
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197: </body>
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