1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<TITLE>BIND options Statement</TITLE>
</HEAD>
<BODY>
<H2>BIND Configuration File Guide -- <CODE>options</CODE> Statement</H2>
<HR>
<A NAME="Syntax"><H3>Syntax</H3></A>
<PRE>
options {
[ version <VAR>version_string</VAR>; ]
[ directory <VAR>path_name</VAR>; ]
[ named-xfer <VAR>path_name</VAR>; ]
[ dump-file <VAR>path_name</VAR>; ]
[ memstatistics-file <VAR>path_name</VAR>; ]
[ pid-file <VAR>path_name</VAR>; ]
[ statistics-file <VAR>path_name</VAR>; ]
[ auth-nxdomain <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ deallocate-on-exit <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ dialup <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ fake-iquery <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ fetch-glue <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ has-old-clients <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ host-statistics <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ multiple-cnames <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ notify <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ recursion <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ rfc2308-type1 <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ use-id-pool <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ treat-cr-as-space <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ also-notify { <VAR><A HREF="docdef.html">ip_addr</A></VAR>; [ <VAR><A HREF="docdef.html">ip_addr</A></VAR>; ... ] }; ]
[ forward ( only | first ); ]
[ forwarders { [ <VAR><A HREF="docdef.html">in_addr</A></VAR> ; [ <VAR><A HREF="docdef.html">in_addr</A></VAR> ; ... ] ] }; ]
[ check-names ( master | slave | response ) ( warn | fail | ignore); ]
[ allow-query { <VAR>address_match_list</VAR> }; ]
[ allow-transfer { <VAR>address_match_list</VAR> }; ]
[ allow-recursion { <VAR>address_match_list</VAR> }; ]
[ blackhole { <VAR>address_match_list</VAR> }; ]
[ listen-on [ port <VAR><A HREF="docdef.html">ip_port</A></VAR> ] { <VAR>address_match_list</VAR> }; ]
[ query-source [ address ( <VAR><A HREF="docdef.html">ip_addr</A></VAR> | * ) ] [ port ( <VAR><A HREF="docdef.html">ip_port</A></VAR> | * ) ] ; ]
[ lame-ttl <VAR>number</VAR>; ]
[ max-transfer-time-in <VAR>number</VAR>; ]
[ max-ncache-ttl <VAR>number</VAR>; ]
[ min-roots <VAR>number</VAR>; ]
[ serial-queries <VAR>number</VAR>; ]
[ transfer-format ( one-answer | many-answers ); ]
[ transfers-in <VAR>number</VAR>; ]
[ transfers-out <VAR>number</VAR>; ]
[ transfers-per-ns <VAR>number</VAR>; ]
[ transfer-source <VAR><A HREF="docdef.html">ip_addr</A></VAR>; ]
[ maintain-ixfr-base <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
[ max-ixfr-log-size <VAR>number</VAR>; ]
[ coresize <VAR><A HREF="docdef.html">size_spec</A></VAR> ; ]
[ datasize <VAR><A HREF="docdef.html">size_spec</A></VAR> ; ]
[ files <VAR><A HREF="docdef.html">size_spec</A></VAR> ; ]
[ stacksize <VAR><A HREF="docdef.html">size_spec</A></VAR> ; ]
[ cleaning-interval <VAR>number</VAR>; ]
[ heartbeat-interval <VAR>number</VAR>; ]
[ interface-interval <VAR>number</VAR>; ]
[ statistics-interval <VAR>number</VAR>; ]
[ <A HREF="#topology">topology</A> { <VAR>address_match_list</VAR> }; ]
[ <A HREF="#sortlist">sortlist</A> { <VAR>address_match_list</VAR> }; ]
[ rrset-order { <VAR>order_spec</VAR> ; [ <VAR>order_spec</VAR> ; ... ] }; ]
};
</PRE>
<HR>
<A NAME="Usage"><H3>Definition and Usage</H3></A>
<P>The options statement sets up global options to be used by
BIND. This statement may appear at only once in a
configuration file; if more than one occurrence is found, the
first occurrence determines the actual options used,
and a warning will be generated. If there is no options statement,
an options block with each option set to its default will be used.</P>
<H4>Pathnames</H4>
<DL>
<DT><CODE>version</CODE>
<DD>
The version the server should report via the <VAR>ndc</VAR> command
or via a query of name <CODE>version.bind</CODE> in class <I>chaos</I>.
The default is the real version number of the server, but some server
operators prefer the string <CODE>"surely you must be joking"</CODE>.
<DT><CODE>directory</CODE>
<DD>
The working directory of the server. Any non-absolute
pathnames in the configuration file will be taken as relative to this
directory. The default location for most server output files
(e.g. "named.run") is this directory. If a directory is not
specified, the working directory defaults to ".", the directory from which the
server was started. The directory specified should be an absolute path.
<DT><CODE>named-xfer</CODE>
<DD>
The pathname to the named-xfer program that the server uses for
inbound zone transfers. If not specified, the default is
system dependent (e.g. "/usr/sbin/named-xfer").
<DT><CODE>dump-file</CODE>
<DD>
The pathname of the file the server dumps the database to when it
receives <CODE>SIGINT</CODE> signal (<CODE>ndc dumpdb</CODE>). If not
specified, the default is "named_dump.db".
<DT><CODE>memstatistics-file</CODE>
<DD>
The pathname of the file the server writes memory usage statistics to, on exit,
if <CODE>deallocate-on-exit</CODE> is <CODE>yes</CODE>. If not
specified, the default is "named.memstats".
<DT><CODE>pid-file</CODE>
<DD>
The pathname of the file the server writes its process ID in. If not
specified, the default is operating system dependent, but is usually
"/var/run/named.pid" or "/etc/named.pid". The pid-file is used by
programs like "ndc" that want to send signals to the running
nameserver.
<DT><CODE>statistics-file</CODE>
<DD>
The pathname of the file the server appends statistics to when it
receives <CODE>SIGILL</CODE> signal (<CODE>ndc stats</CODE>). If not
specified, the default is "named.stats".
</DL>
<A name="BooleanOptions"><H4>Boolean Options</H4></A>
<DL>
<DT><CODE>auth-nxdomain</CODE>
<DD>
If <CODE>yes</CODE>, the <CODE>AA</CODE> bit is always set on
NXDOMAIN responses, even if the server is not actually authoritative.
The default is <CODE>yes</CODE>. Do not turn off
<CODE>auth-nxdomain</CODE> unless you are sure you know what you are
doing, as some older software won't like it.
<DT><CODE>deallocate-on-exit</CODE>
<DD>
If <CODE>yes</CODE>, the server will painstakingly deallocate every object it
it allocated, when it exits, and then write a memory usage report to
the <CODE>memstatistics-file</CODE>. The default is <CODE>no</CODE>, because
it is faster to let the operating system clean up.
<CODE>deallocate-on-exit</CODE> is handy for detecting memory leaks.
<DT><CODE>dialup</CODE>
<DD>
If <CODE>yes</CODE>, the server treats all zones as if they are
doing zone transfers across a dial on demand dialup link, which can
be brought up by traffic originating from this server. This has
different effects according to zone type and concentrates the zone
maintenance so that it all happens in a short interval, once every
<CODE>heartbeat-interval</CODE> and hopefully during the one call.
It also suppresses some of the normal zone maintainance traffic.
The default is <CODE>no</CODE>. The <CODE>dialup</CODE>
option may also be specified in the <CODE>zone</CODE> statement, in which
case it overrides the <CODE>options dialup</CODE> statement.
<P>
If the zone is a <CODE>master</CODE> zone, the server will send out
NOTIFY request to all the slaves. This will trigger the "zone up to
date checking" in the slave (providing it supports NOTIFY), allowing
the <CODE>slave</CODE> to verify the zone while the call us up.
<P>
If the zone is a <CODE>slave</CODE> or <CODE>stub</CODE> zone, the server
will suppress the regular "zone up to date" queries and only perform
them when the <CODE>heartbeat-interval</CODE> expires.
<DT><CODE>fake-iquery</CODE>
<DD>
If <CODE>yes</CODE>, the server will simulate the obsolete DNS query type
IQUERY. The default is <CODE>no</CODE>.
<DT><CODE>fetch-glue</CODE>
<DD>
If <CODE>yes</CODE> (the default), the server will fetch "glue" resource
records it doesn't have when constructing the additional data section of
a response. <CODE>fetch-glue no</CODE> can be used in conjunction with
<CODE>recursion no</CODE> to prevent the server's cache from growing or
becoming corrupted (at the cost of requiring more work from the client).
<DT><CODE>has-old-clients</CODE>
<DD>
Setting the option to <CODE>yes</CODE> is equivalent to setting the following
options: <CODE>auth-nxdomain yes;</CODE> and <CODE>rfc2308-type1 no;</CODE>.
The use of <CODE>has-old-clients</CODE> with <CODE>auth-nxdomain</CODE>
and <CODE>rfc2308-type1</CODE> is order dependent.
<DT><CODE>host-statistics</CODE>
<DD>
If <CODE>yes</CODE>, statistics are kept for every host that the
the nameserver interacts with. The default is <CODE>no</CODE>. <I>Note:</I>
turning on <CODE>host-statistics</CODE> can consume huge amounts of memory.
<DT><CODE>maintain-ixfr-base</CODE>
<DD>
If <CODE>yes</CODE>, a transaction log is kept for
Incremental Zone Transfer. The default is <CODE>no</CODE>.
<DT><CODE>multiple-cnames</CODE>
<DD>
If <CODE>yes</CODE>, multiple CNAME resource records will be
allowed for a domain name. The default is <CODE>no</CODE>. Allowing
multiple CNAME records is against standards and is not recommended.
Multiple CNAME support is available because previous versions of BIND
allowed multiple CNAME records, and these records have been used for load
balancing by a number of sites.
<DT><CODE>notify</CODE>
<DD>
If <CODE>yes</CODE> (the default), DNS NOTIFY messages are sent when a
zone the server is authoritative for changes. The use of NOTIFY
speeds convergence between the master and its slaves. Slave servers
that receive a NOTIFY message, and understand it, will contact the
master server for the zone to see if they need to do a zone transfer. If
they do, they will initiate it immediately. The <CODE>notify</CODE>
option may also be specified in the <CODE>zone</CODE> statement, in which
case it overrides the <CODE>options notify</CODE> statement.
<DT><CODE>recursion</CODE>
<DD>
If <CODE>yes</CODE>, and a DNS query requests recursion, the
server will attempt to do all the work required to answer the query.
If recursion is not on, the server will return a referral to the
client if it doesn't know the answer. The default is <CODE>yes</CODE>.
See also <CODE>fetch-glue</CODE> above.
<DT><CODE>rfc2308-type1</CODE>
<DD>
If <CODE>yes</CODE>, the server will send NS records along with the SOA
record for negative answers.
You need to set this to <CODE>no</CODE> if you have an old BIND
server using you as a forwarder that does not understand negative answers
which contain both SOA and NS records or you have an old version of sendmail.
The correct fix is to upgrade the broken server or sendmail.
The default is <CODE>no</CODE>.
<DT><CODE>use-id-pool</CODE>
<DD>
If <CODE>yes</CODE>, the server will keep track of its own outstanding
query ID's to avoid duplication and increase randomness. This will result
in 128KB more memory being consumed by the server.
The default is <CODE>no</CODE>.
<DT><CODE>treat-cr-as-space</CODE>
<DD>
If <CODE>yes</CODE>, the server will treat '\r' characters the same way it
treats a ' ' or '\t'. This may be necessary when loading zone files on a
UNIX system that were generated on an NT or DOS machine. The default is <CODE>no</CODE>.
</DL>
<A NAME="Also-notify"><H4>Also-Notify</H4></A>
<DT><CODE>also-notify</CODE>
<P>
Defines a global list of IP addresses that also get sent NOTIFY messages
whenever a fresh copy of the zone is loaded. This helps to ensure that
copies of the zones will quickly converge on ``stealth'' servers.
If an <CODE>also-notify</CODE> list is given in a <CODE>zone</CODE>
statement, it will override the <CODE>options also-notify</CODE> statement.
When a <CODE>zone notify</CODE> statement is set to <CODE>no</CODE>,
the IP addresses in the global <CODE>also-notify</CODE> list will not get
sent NOTIFY messages for that zone.
The default is the empty list (no global notification list).
<A NAME="Forwarding"><H4>Forwarding</H4></A>
<P>The forwarding facility can be used to create a large site-wide
cache on a few servers, reducing traffic over links to external
nameservers. It can also be used to allow queries by servers that do
not have direct access to the Internet, but wish to look up exterior
names anyway. Forwarding occurs only on those queries for which the
server is not authoritative and does not have the answer in its cache.
<DL>
<DT><CODE>forward</CODE>
<DD>
This option is only meaningful if the <CODE>forwarders</CODE> list is
not empty. A value of <CODE>first</CODE>, the default, causes the
server to query the forwarders first, and if that doesn't answer the
question the server will then look for the answer itself. If
<CODE>only</CODE> is specified, the server will only query the
forwarders.
<DT><CODE>forwarders</CODE>
<DD>
Specifies the IP addresses to be used for forwarding. The default is the
empty list (no forwarding).
</DL>
<P>Forwarding can also be configured on a per-zone basis, allowing for
the global forwarding options to be overridden in a variety of ways.
You can set particular zones to use different forwarders, or have
different <CODE>forward only/first</CODE> behavior, or to not forward
at all. See the <A HREF="zone.html"><CODE>zone</CODE></A> statement
for more information.
<P>Future versions of BIND 8 will provide a more powerful forwarding
system. The syntax described above will continue to be supported.
<a name="NameChecking"><H4>Name Checking</H4></a>
<P>The server can check domain names based upon their expected client contexts.
For example, a domain name used as a hostname can be checked for compliance
with the RFCs defining valid hostnames.
<P>Three checking methods are available:
<DL>
<DT><CODE>ignore</CODE>
<DD>
No checking is done.
<DT><CODE>warn</CODE>
<DD>
Names are checked against their expected client contexts. Invalid names are
logged, but processing continues normally.
<DT><CODE>fail</CODE>
<DD>
Names are checked against their expected client contexts. Invalid names are
logged, and the offending data is rejected.
</DL>
<P>The server can check names three areas: master zone files, slave
zone files, and in responses to queries the server has initiated. If
<CODE>check-names response fail</CODE> has been specified, and
answering the client's question would require sending an invalid name
to the client, the server will send a REFUSED response code to the
client.
<P>The defaults are:
<PRE>
check-names master fail;
check-names slave warn;
check-names response ignore;
</PRE>
<P><CODE>check-names</CODE> may also be specified in the
<A HREF="zone.html"><CODE>zone</CODE></A>
statement, in which case it overrides the <CODE>options check-names</CODE>
statement. When used in a <CODE>zone</CODE> statement, the area is not
specified (because it can be deduced from the zone type).
<A name="AccessControl"><H4>Access Control</H4></A>
<P>Access to the server can be restricted based on the IP address of the
requesting system. See
<VAR><A HREF="address_list.html">address_match_list</A></VAR> for details
on how to specify IP address lists.
<DL>
<DT><CODE>allow-query</CODE>
<DD>
Specifies which hosts are allowed to ask ordinary questions.
<CODE>allow-query</CODE> may also be specified in the
<CODE>zone</CODE> statement, in which case it overrides the
<CODE>options allow-query</CODE> statement. If not specified, the default is
to allow queries from all hosts.
<DT><CODE>allow-transfer</CODE>
<DD>
Specifies which hosts are allowed to receive zone transfers from the
server. <CODE>allow-transfer</CODE> may also be specified in the
<CODE>zone</CODE> statement, in which case it overrides the
<CODE>options allow-transfer</CODE> statement. If not specified, the default
is to allow transfers from all hosts.
<DT><CODE>allow-recursion</CODE>
<DD>
Specifies which hosts are allowed to make recursive queries through this
server. If not specified, the default is to allow recursive queries from
all hosts.
<DT><CODE>blackhole</CODE>
<DD>
Specifies a list of addresses that the server will not accept queries from
or use to resolve a query. Queries from these addresses will not be
responded to.
</DL>
<H4>Interfaces</H4>
<P>The interfaces and ports that the server will answer queries from may
be specified using the <CODE>listen-on</CODE> option. <CODE>listen-on</CODE>
takes an optional port, and an
<VAR><A HREF="address_list.html">address_match_list</A></VAR>. The server will
listen on all interfaces allowed by the address match list. If a port is
not specified, port 53 will be used.
<P>Multiple <CODE>listen-on</CODE> statements are allowed. For example,
<PRE>
listen-on { 5.6.7.8; };
listen-on port 1234 { !1.2.3.4; 1.2/16; };
</PRE>
will enable the nameserver on port 53 for the IP address 5.6.7.8, and
on port 1234 of an address on the machine in net 1.2 that is not
1.2.3.4.
<P>If no <CODE>listen-on</CODE> is specified, the server will listen on port
53 on all interfaces.
<H4>Query Address</H4>
<P>If the server doesn't know the answer to a question, it will query
other nameservers. <CODE>query-source</CODE> specifies the address
and port used for such queries. If <CODE>address</CODE> is
<CODE>*</CODE> or is omitted, a wildcard IP address
(<CODE>INADDR_ANY</CODE>) will be used. If <CODE>port</CODE> is
<CODE>*</CODE> or is omitted, a random unprivileged port will be used.
The default is
<PRE>
query-source address * port *;
</PRE>
<P>Note: <CODE>query-source</CODE> currently applies only to UDP queries;
TCP queries always use a wildcard IP address and a random unprivileged
port.
<A name="ZoneTransfers"><H4>Zone Transfers</H4></A>
<DL>
<DT><CODE>max-transfer-time-in</CODE>
<DD>
Inbound zone transfers (<CODE>named-xfer</CODE> processes) running
longer than this many minutes will be terminated. The default is 120
minutes (2 hours).
<DT><CODE>transfer-format</CODE>
<DD>
The server supports two zone transfer methods.
<CODE>one-answer</CODE> uses one DNS message per resource record
transferred. <CODE>many-answers</CODE> packs as many resource records
as possible into a message. <CODE>many-answers</CODE> is more
efficient, but is only known to be understood by BIND 8.1+ and patched
versions of BIND 4.9.5. The default is <CODE>one-answer</CODE>.
<CODE>transfer-format</CODE> may be
overridden on a per-server basis by using the <CODE>server</CODE> statement.
<DT><CODE>transfers-in</CODE>
<DD>
The maximum number of inbound zone transfers that can be running
concurrently. The default value is 10. Increasing
<CODE>transfers-in</CODE> may speed up the convergence of slave zones,
but it also may increase the load on the local system.
<DT><CODE>transfers-out</CODE>
<DD>
This option will be used in the future to limit the number of
concurrent outbound zone transfers. It is checked for syntax, but is
otherwise ignored.
<DT><CODE>transfers-per-ns</CODE>
<DD>
The maximum number of inbound zone transfers (<CODE>named-xfer</CODE>
processes) that can be concurrently transferring from a given remote
nameserver. The default value is 2. Increasing
<CODE>transfers-per-ns</CODE> may speed up the convergence of slave
zones, but it also may increase the load on the remote nameserver.
<CODE>transfers-per-ns</CODE> may be overridden on a per-server basis
by using the <CODE>transfers</CODE> phrase of the <CODE>server</CODE>
statement.
<DT><CODE>transfer-source</CODE>
<DD>
<CODE>transfer-source</CODE> determines which local address will be bound
to the TCP connection used to fetch all zones transferred inbound by the
server. If not set, it defaults to a system controlled value which will
usually be the address of the interface ``closest to'' the remote end.
This address must appear in the remote end's <CODE>allow-transfer</CODE>
option for the zone being transferred, if one is specified. This statement
sets the <CODE>transfer-source</CODE> for all zones, but can be overridden
on a per-zone basis by including a <CODE>transfer-source</CODE> statement
within the zone block in the configuration file.
<DT><CODE>serial-queries</CODE>
<DD>
Slave servers will periodically query master servers to find out if zone
serial numbers have changed. Each such query uses a minute amount of the
slave server's network bandwidth, but more importantly each query uses a
small amount of <I>memory</I> in the slave server while waiting for the
master server to respond. The <CODE>serial-queries</CODE> option sets the
maximum number of concurrent serial-number queries allowed to be outstanding
at any given time. The default is four (4).
<B>Note:</B>
If a server loads a large (tens or hundreds of thousands) number of slave
zones, this limit should be raised to the high hundreds or low
thousands -- otherwise the slave server may never actually become aware of
zone changes in the master servers. Beware, though, that setting this limit
arbitrarily high can spend a considerable amount of your slave server's
network, CPU, and memory resources. As with all tunable limits, this one
should be changed gently and monitored for its effects.
</DL>
<H4>Resource Limits</H4>
<P>The server's usage of many system resources can be limited. Some
operating systems don't support some of the limits. On such systems,
a warning will be issued if the unsupported limit is used. Some
operating systems don't support limiting resources, and on these systems
a <CODE>cannot set resource limits on this system</CODE> message will
be logged.
<P>Scaled values are allowed when specifying resource limits. For
example, <CODE>1G</CODE> can be used instead of
<CODE>1073741824</CODE> to specify a limit of one gigabyte.
<CODE>unlimited</CODE> requests unlimited use, or the maximum
available amount. <CODE>default</CODE> uses the limit that was in
force when the server was started. See
<VAR><A HREF="docdef.html">size_spec</A></VAR> for more details.
<DL>
<DT><CODE>coresize</CODE>
<DD>
The maximum size of a core dump. The default is <CODE>default</CODE>.
<DT><CODE>datasize</CODE>
<DD>
The maximum amount of data memory the server may use. The default is
<CODE>default</CODE>.
<DT><CODE>files</CODE>
<DD>
The maximum number of files the server may have open concurrently.
The default is <CODE>unlimited</CODE>. <I>Note:</I> on some operating
systems the server cannot set an unlimited value and cannot determine
the maximum number of open files the kernel can support. On such
systems, choosing <CODE>unlimited</CODE> will cause the server to use
the larger of the <CODE>rlim_max</CODE> for <CODE>RLIMIT_NOFILE</CODE>
and the value returned by <CODE>sysconf(_SC_OPEN_MAX)</CODE>. If the
actual kernel limit is larger than this value, use <CODE>limit
files</CODE> to specify the limit explicitly.
<DT><CODE>max-ixfr-log-size</CODE>
<DD>
The <CODE>max-ixfr-log-size</CODE> will be used in a future release of
the server to limit the size of the
transaction log kept for Incremental Zone Transfer.
<DT><CODE>stacksize</CODE>
<DD>
The maximum amount of stack memory the server may use. The default is
<CODE>default</CODE>.
</DL>
<H4>Periodic Task Intervals</H4>
<DL>
<DT><CODE>cleaning-interval</CODE>
<DD>
The server will remove expired resource records from the cache every
<CODE>cleaning-interval</CODE> minutes. The default is 60 minutes. If set
to 0, no periodic cleaning will occur.
<DT><CODE>heartbeat-interval</CODE>
<DD>
The server will perform zone maintenance tasks for all zones marked
<CODE>dialup yes</CODE> whenever this interval expires.
The default is 60 minutes. Reasonable values are up to 1 day (1440 minutes).
If set to 0, no zone maintenance for these zones will occur.
<DT><CODE>interface-interval</CODE>
<DD>
The server will scan the network interface list every
<CODE>interface-interval</CODE> minutes. The default is 60 minutes.
If set to 0, interface scanning will only occur when the configuration
file is loaded. After the scan, listeners will be started on any new
interfaces (provided they are allowed by the <CODE>listen-on</CODE>
configuration). Listeners on interfaces that have gone away will be
cleaned up.
<DT><CODE>statistics-interval</CODE>
<DD>
Nameserver statistics will be logged every <CODE>statistics-interval</CODE>
minutes. The default is 60. If set to 0, no statistics will be logged.
</DL>
<H4><A NAME="topology">Topology</A></H4>
<P>All other things being equal, when the server chooses a nameserver
to query from a list of nameservers, it prefers the one that is
topologically closest to itself. The <CODE>topology</CODE> statement
takes an <VAR><A HREF="address_list.html">address_match_list</A></VAR>
and interprets it in a special way. Each top-level list element is
assigned a distance. Non-negated elements get a distance based on
their position in the list, where the closer the match is to the start
of the list, the shorter the distance is between it and the server. A
negated match will be assigned the maximum distance from the server.
If there is no match, the address will get a distance which is further
than any non-negated list element, and closer than any negated
element. For example,
<PRE>
topology {
10/8;
!1.2.3/24;
{ 1.2/16; 3/8; };
};
</PRE>
<P>will prefer servers on network 10 the most, followed by hosts on
network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the exception
of hosts on network 1.2.3 (netmask 255.255.255.0), which is preferred least
of all.
<P>The default topology is
<PRE>
topology { localhost; localnets; };
</PRE>
<H4><A NAME="sortlist">Resource Record sorting</A></H4>
<P>
When returning multiple RRs,
the nameserver will normally return them in
<B>Round Robin</B>,
i.e. after each request, the first RR is put to the end of the list.
As the order of RRs is not defined, this should not cause any problems.
</P>
<P>
The client resolver code should re-arrange the RRs as appropriate,
i.e. using any addresses on the local net in preference to other addresses.
However, not all resolvers can do this, or are not correctly configured.
</P>
<P>
When a client is using a local server, the sorting can be performed in the
server, based on the client's address.
This only requires configuring the nameservers, not all the clients.
</P>
<P>
The sortlist statement takes an address match list and interprets it even
more specially than the <A HREF="#topology">topology</A> statement does.
</P>
<P>
Each top level statement in the sortlist must itself be an explicit
address match list with one or two elements. The first element
(which may be an IP address, an IP prefix, an ACL name or nested
address match list) of each top level list is checked against the
source address of the query until a match is found.
</P>
<P>
Once the source address of the query has been matched, if the top level
statement contains only one element, the actual primitive element that
matched the source address is used to select the address in the response
to move to the beginning of the response. If the statement is a list
of two elements, the second element is treated like the address
match list in a topology statement. Each top level element is assigned
a distance and the address in the response with the minimum distance is
moved to the beginning of the response.
</P>
<P>
In the following example, any queries received from any of the addresses
of the host itself will get responses preferring addresses on any of
the locally connected networks. Next most preferred are addresses on
the 192.168.1/24 network, and after that either the 192.168.2/24 or
192.168.3/24 network with no preference shown between these two networks.
Queries received from a host on the 192.168.1/24 network will prefer
other addresses on that network to the 192.168.2/24 and 192.168.3/24
networks. Queries received from a host on the 192.168.4/24 or the
192.168.5/24 network will only prefer other addresses on their
directly connected networks.
<PRE>
sortlist {
{ localhost; // IF the local host
{ localnets; // THEN first fit on the
192.168.1/24; // following nets
{ 192,168.2/24; 192.168.3/24; }; }; };
{ 192.168.1/24; // IF on class C 192.168.1
{ 192.168.1/24; // THEN use .1, or .2 or .3
{ 192.168.2/24; 192.168.3/24; }; }; };
{ 192.168.2/24; // IF on class C 192.168.2
{ 192.168.2/24; // THEN use .2, or .1 or .3
{ 192.168.1/24; 192.168.3/24; }; }; };
{ 192.168.3/24; // IF on class C 192.168.3
{ 192.168.3/24; // THEN use .3, or .1 or .2
{ 192.168.1/24; 192.168.2/24; }; }; };
{ { 192.168.4/24; 192.168.5/24; }; // if .4 or .5, prefer that net
};
};
</PRE>
The following example will give reasonable behaviour for the local host
and hosts on directly connected networks. It is similar to the behavior
of the address sort in BIND 4.9.x. Responses sent to queries from the
local host will favor any of the directly connected networks. Responses
sent to queries from any other hosts on a directly connected network will
prefer addresses on that same network. Responses to other queries will
not be sorted.
<PRE>
sortlist {
{ localhost; localnets; };
{ localnets; };
};
</PRE>
<!--
* XXX - it would be nice to have an ACL called "source" that matched the
* source address of a query so that a host could be configured to
* automatically prefer itself, and an ACL called "sourcenet", that
* would return the primitive IP match element that matched the source
* address so that you could do:
* { localnets; { sourcenet; { other stuff ...}; };
* and automatically get similar behaviour to what you get with:
* { localnets; };
-->
</P>
<a name="RrsetOrder">
<H4>RRset Ordering</H4>
<P>When multiple records are returned in an answer it may be useful to
configure the order the records are placed into the response. For example the
records for a zone might be configured to always be returned in the order they
are defined in the zone file. Or perhaps a <i>random</i> shuffle of the
records as they are returned is wanted. The <var>rrset-order</var> statement
permits configuration of the ordering made of the records in a multiple record
response. The default, if no ordering is defined, is a cyclic ordering (round
robin).
<P>An <var>order_spec</var> is defined as follows:
<PRE>
[ <var>class</var> class_name ][ <var>type</var> type_name ][ <var>name</var> "FQDN" ] <var>order</var> ordering
</PRE>
<P>If no <var>class</var> is specified, the default is <code>ANY</code>. If no
<var>type</var> is specified, the default is <code>ANY</code>. If no
<var>name</var> is specified, the default is <code>"*"</code>.
<P>The legal values for <code>ordering</code> are:
<DL>
<DT><code>fixed</code>
<DD>Records are returned in the order they are defined in the zone file.
<DT><code>random</code>
<DD>Records are returned in some random order.
<DT><code>cyclic</code>
<DD>Records are returned in a round-robin order.
</DL>
<P>For example:
<PRE>
rrset-order {
class IN type A name "rc.vix.com" order random;
order cyclic;
};
</PRE>
<P>will cause any responses for type <VAR>A</VAR> records in class
<VAR>IN</VAR> that have "rc.vix.com" as a suffix, to always be returned in
random order. All other records are returned in cyclic order.
<P>If multiple <code>rrset-order</code> statements appear, they are not
combined--the last one applies.
<P>If no <code>rrset-order</code> statement is specified, a default one
of:
<pre>
rrset-order { class ANY type ANY name "*" order cyclic ; };
</pre>
<P>is used.
<H4>Tuning</H4>
<DL>
<DT><CODE>lame-ttl</CODE>
<DD>
Sets the number of seconds to cache a lame server indication.
0 disables caching. Default is 600 (10 minutes). Maximum value is 1800 (30 minutes).
<DT><CODE>max-ncache-ttl</CODE>
<DD>
To reduce network traffic and increase performance the server stores negative
answers. <CODE>max-ncache-ttl</CODE> is used to set a maximum retention time
for these answers in the server is seconds. The default <CODE>max-ncache-ttl</CODE> is
10800 seconds (3 hours). <CODE>max-ncache-ttl</CODE> cannot exceed the
maximum retention time for ordinary (positive) answers (7 days) and will be
silently truncated to 7 days if set to a value which is greater that 7 days.
<DT><CODE>min-roots</CODE>
<DD>
The minimum number of root servers that is required for a
request for the root servers to be accepted. Default 2.
</DL>
<HR>
<CENTER><P>[ <A HREF="config.html">BIND Config. File</A>
| <A HREF="http://www.isc.org/products/BIND/">BIND Home</A>
| <A HREF="http://www.isc.org/">ISC</A> ]</P></CENTER>
<HR>
<ADDRESS>
Last Updated: $Id: options.html,v 1.40 2000/06/01 21:37:46 cyarnell Exp $
</ADDRESS>
</BODY>
</HTML>
|
