| blob | d46338af6002997b0593d4875a6aee825c77126f |
1 /proc/sys/net/ipv4/* Variables:
3 ip_forward - BOOLEAN
4 0 - disabled (default)
5 not 0 - enabled
7 Forward Packets between interfaces.
9 This variable is special, its change resets all configuration
10 parameters to their default state (RFC1122 for hosts, RFC1812
11 for routers)
13 ip_default_ttl - INTEGER
14 default 64
16 ip_no_pmtu_disc - BOOLEAN
17 Disable Path MTU Discovery.
18 default FALSE
20 min_pmtu - INTEGER
21 default 562 - minimum discovered Path MTU
23 mtu_expires - INTEGER
24 Time, in seconds, that cached PMTU information is kept.
26 min_adv_mss - INTEGER
27 The advertised MSS depends on the first hop route MTU, but will
28 never be lower than this setting.
30 IP Fragmentation:
32 ipfrag_high_thresh - INTEGER
33 Maximum memory used to reassemble IP fragments. When
34 ipfrag_high_thresh bytes of memory is allocated for this purpose,
35 the fragment handler will toss packets until ipfrag_low_thresh
36 is reached.
38 ipfrag_low_thresh - INTEGER
39 See ipfrag_high_thresh
41 ipfrag_time - INTEGER
42 Time in seconds to keep an IP fragment in memory.
44 ipfrag_secret_interval - INTEGER
45 Regeneration interval (in seconds) of the hash secret (or lifetime
46 for the hash secret) for IP fragments.
47 Default: 600
49 ipfrag_max_dist - INTEGER
50 ipfrag_max_dist is a non-negative integer value which defines the
51 maximum "disorder" which is allowed among fragments which share a
52 common IP source address. Note that reordering of packets is
53 not unusual, but if a large number of fragments arrive from a source
54 IP address while a particular fragment queue remains incomplete, it
55 probably indicates that one or more fragments belonging to that queue
56 have been lost. When ipfrag_max_dist is positive, an additional check
57 is done on fragments before they are added to a reassembly queue - if
58 ipfrag_max_dist (or more) fragments have arrived from a particular IP
59 address between additions to any IP fragment queue using that source
60 address, it's presumed that one or more fragments in the queue are
61 lost. The existing fragment queue will be dropped, and a new one
62 started. An ipfrag_max_dist value of zero disables this check.
64 Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
65 result in unnecessarily dropping fragment queues when normal
66 reordering of packets occurs, which could lead to poor application
67 performance. Using a very large value, e.g. 50000, increases the
68 likelihood of incorrectly reassembling IP fragments that originate
69 from different IP datagrams, which could result in data corruption.
70 Default: 64
72 INET peer storage:
74 inet_peer_threshold - INTEGER
75 The approximate size of the storage. Starting from this threshold
76 entries will be thrown aggressively. This threshold also determines
77 entries' time-to-live and time intervals between garbage collection
78 passes. More entries, less time-to-live, less GC interval.
80 inet_peer_minttl - INTEGER
81 Minimum time-to-live of entries. Should be enough to cover fragment
82 time-to-live on the reassembling side. This minimum time-to-live is
83 guaranteed if the pool size is less than inet_peer_threshold.
84 Measured in jiffies(1).
86 inet_peer_maxttl - INTEGER
87 Maximum time-to-live of entries. Unused entries will expire after
88 this period of time if there is no memory pressure on the pool (i.e.
89 when the number of entries in the pool is very small).
90 Measured in jiffies(1).
92 inet_peer_gc_mintime - INTEGER
93 Minimum interval between garbage collection passes. This interval is
94 in effect under high memory pressure on the pool.
95 Measured in jiffies(1).
97 inet_peer_gc_maxtime - INTEGER
98 Minimum interval between garbage collection passes. This interval is
99 in effect under low (or absent) memory pressure on the pool.
100 Measured in jiffies(1).
102 TCP variables:
104 tcp_abc - INTEGER
105 Controls Appropriate Byte Count defined in RFC3465. If set to
106 0 then does congestion avoid once per ack. 1 is conservative
107 value, and 2 is more agressive.
109 tcp_syn_retries - INTEGER
110 Number of times initial SYNs for an active TCP connection attempt
111 will be retransmitted. Should not be higher than 255. Default value
112 is 5, which corresponds to ~180seconds.
114 tcp_synack_retries - INTEGER
115 Number of times SYNACKs for a passive TCP connection attempt will
116 be retransmitted. Should not be higher than 255. Default value
117 is 5, which corresponds to ~180seconds.
119 tcp_keepalive_time - INTEGER
120 How often TCP sends out keepalive messages when keepalive is enabled.
121 Default: 2hours.
123 tcp_keepalive_probes - INTEGER
124 How many keepalive probes TCP sends out, until it decides that the
125 connection is broken. Default value: 9.
127 tcp_keepalive_intvl - INTEGER
128 How frequently the probes are send out. Multiplied by
129 tcp_keepalive_probes it is time to kill not responding connection,
130 after probes started. Default value: 75sec i.e. connection
131 will be aborted after ~11 minutes of retries.
133 tcp_retries1 - INTEGER
134 How many times to retry before deciding that something is wrong
135 and it is necessary to report this suspicion to network layer.
136 Minimal RFC value is 3, it is default, which corresponds
137 to ~3sec-8min depending on RTO.
139 tcp_retries2 - INTEGER
140 How may times to retry before killing alive TCP connection.
141 RFC1122 says that the limit should be longer than 100 sec.
142 It is too small number. Default value 15 corresponds to ~13-30min
143 depending on RTO.
145 tcp_orphan_retries - INTEGER
146 How may times to retry before killing TCP connection, closed
147 by our side. Default value 7 corresponds to ~50sec-16min
148 depending on RTO. If you machine is loaded WEB server,
149 you should think about lowering this value, such sockets
150 may consume significant resources. Cf. tcp_max_orphans.
152 tcp_fin_timeout - INTEGER
153 Time to hold socket in state FIN-WAIT-2, if it was closed
154 by our side. Peer can be broken and never close its side,
155 or even died unexpectedly. Default value is 60sec.
156 Usual value used in 2.2 was 180 seconds, you may restore
157 it, but remember that if your machine is even underloaded WEB server,
158 you risk to overflow memory with kilotons of dead sockets,
159 FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1,
160 because they eat maximum 1.5K of memory, but they tend
161 to live longer. Cf. tcp_max_orphans.
163 tcp_max_tw_buckets - INTEGER
164 Maximal number of timewait sockets held by system simultaneously.
165 If this number is exceeded time-wait socket is immediately destroyed
166 and warning is printed. This limit exists only to prevent
167 simple DoS attacks, you _must_ not lower the limit artificially,
168 but rather increase it (probably, after increasing installed memory),
169 if network conditions require more than default value.
171 tcp_tw_recycle - BOOLEAN
172 Enable fast recycling TIME-WAIT sockets. Default value is 0.
173 It should not be changed without advice/request of technical
174 experts.
176 tcp_tw_reuse - BOOLEAN
177 Allow to reuse TIME-WAIT sockets for new connections when it is
178 safe from protocol viewpoint. Default value is 0.
179 It should not be changed without advice/request of technical
180 experts.
182 tcp_max_orphans - INTEGER
183 Maximal number of TCP sockets not attached to any user file handle,
184 held by system. If this number is exceeded orphaned connections are
185 reset immediately and warning is printed. This limit exists
186 only to prevent simple DoS attacks, you _must_ not rely on this
187 or lower the limit artificially, but rather increase it
188 (probably, after increasing installed memory),
189 if network conditions require more than default value,
190 and tune network services to linger and kill such states
191 more aggressively. Let me to remind again: each orphan eats
192 up to ~64K of unswappable memory.
194 tcp_abort_on_overflow - BOOLEAN
195 If listening service is too slow to accept new connections,
196 reset them. Default state is FALSE. It means that if overflow
197 occurred due to a burst, connection will recover. Enable this
198 option _only_ if you are really sure that listening daemon
199 cannot be tuned to accept connections faster. Enabling this
200 option can harm clients of your server.
202 tcp_syncookies - BOOLEAN
203 Only valid when the kernel was compiled with CONFIG_SYNCOOKIES
204 Send out syncookies when the syn backlog queue of a socket
205 overflows. This is to prevent against the common 'syn flood attack'
206 Default: FALSE
208 Note, that syncookies is fallback facility.
209 It MUST NOT be used to help highly loaded servers to stand
210 against legal connection rate. If you see synflood warnings
211 in your logs, but investigation shows that they occur
212 because of overload with legal connections, you should tune
213 another parameters until this warning disappear.
214 See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
216 syncookies seriously violate TCP protocol, do not allow
217 to use TCP extensions, can result in serious degradation
218 of some services (f.e. SMTP relaying), visible not by you,
219 but your clients and relays, contacting you. While you see
220 synflood warnings in logs not being really flooded, your server
221 is seriously misconfigured.
223 tcp_stdurg - BOOLEAN
224 Use the Host requirements interpretation of the TCP urg pointer field.
225 Most hosts use the older BSD interpretation, so if you turn this on
226 Linux might not communicate correctly with them.
227 Default: FALSE
229 tcp_max_syn_backlog - INTEGER
230 Maximal number of remembered connection requests, which are
231 still did not receive an acknowledgment from connecting client.
232 Default value is 1024 for systems with more than 128Mb of memory,
233 and 128 for low memory machines. If server suffers of overload,
234 try to increase this number.
236 tcp_window_scaling - BOOLEAN
237 Enable window scaling as defined in RFC1323.
239 tcp_timestamps - BOOLEAN
240 Enable timestamps as defined in RFC1323.
242 tcp_sack - BOOLEAN
243 Enable select acknowledgments (SACKS).
245 tcp_fack - BOOLEAN
246 Enable FACK congestion avoidance and fast retransmission.
247 The value is not used, if tcp_sack is not enabled.
249 tcp_dsack - BOOLEAN
250 Allows TCP to send "duplicate" SACKs.
252 tcp_ecn - BOOLEAN
253 Enable Explicit Congestion Notification in TCP.
255 tcp_reordering - INTEGER
256 Maximal reordering of packets in a TCP stream.
257 Default: 3
259 tcp_retrans_collapse - BOOLEAN
260 Bug-to-bug compatibility with some broken printers.
261 On retransmit try to send bigger packets to work around bugs in
262 certain TCP stacks.
264 tcp_wmem - vector of 3 INTEGERs: min, default, max
265 min: Amount of memory reserved for send buffers for TCP socket.
266 Each TCP socket has rights to use it due to fact of its birth.
267 Default: 4K
269 default: Amount of memory allowed for send buffers for TCP socket
270 by default. This value overrides net.core.wmem_default used
271 by other protocols, it is usually lower than net.core.wmem_default.
272 Default: 16K
274 max: Maximal amount of memory allowed for automatically selected
275 send buffers for TCP socket. This value does not override
276 net.core.wmem_max, "static" selection via SO_SNDBUF does not use this.
277 Default: 128K
279 tcp_rmem - vector of 3 INTEGERs: min, default, max
280 min: Minimal size of receive buffer used by TCP sockets.
281 It is guaranteed to each TCP socket, even under moderate memory
282 pressure.
283 Default: 8K
285 default: default size of receive buffer used by TCP sockets.
286 This value overrides net.core.rmem_default used by other protocols.
287 Default: 87380 bytes. This value results in window of 65535 with
288 default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
289 less for default tcp_app_win. See below about these variables.
291 max: maximal size of receive buffer allowed for automatically
292 selected receiver buffers for TCP socket. This value does not override
293 net.core.rmem_max, "static" selection via SO_RCVBUF does not use this.
294 Default: 87380*2 bytes.
296 tcp_mem - vector of 3 INTEGERs: min, pressure, max
297 low: below this number of pages TCP is not bothered about its
298 memory appetite.
300 pressure: when amount of memory allocated by TCP exceeds this number
301 of pages, TCP moderates its memory consumption and enters memory
302 pressure mode, which is exited when memory consumption falls
303 under "low".
305 high: number of pages allowed for queueing by all TCP sockets.
307 Defaults are calculated at boot time from amount of available
308 memory.
310 tcp_app_win - INTEGER
311 Reserve max(window/2^tcp_app_win, mss) of window for application
312 buffer. Value 0 is special, it means that nothing is reserved.
313 Default: 31
315 tcp_adv_win_scale - INTEGER
316 Count buffering overhead as bytes/2^tcp_adv_win_scale
317 (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
318 if it is <= 0.
319 Default: 2
321 tcp_rfc1337 - BOOLEAN
322 If set, the TCP stack behaves conforming to RFC1337. If unset,
323 we are not conforming to RFC, but prevent TCP TIME_WAIT
324 assassination.
325 Default: 0
327 tcp_low_latency - BOOLEAN
328 If set, the TCP stack makes decisions that prefer lower
329 latency as opposed to higher throughput. By default, this
330 option is not set meaning that higher throughput is preferred.
331 An example of an application where this default should be
332 changed would be a Beowulf compute cluster.
333 Default: 0
335 tcp_tso_win_divisor - INTEGER
336 This allows control over what percentage of the congestion window
337 can be consumed by a single TSO frame.
338 The setting of this parameter is a choice between burstiness and
339 building larger TSO frames.
340 Default: 3
342 tcp_frto - BOOLEAN
343 Enables F-RTO, an enhanced recovery algorithm for TCP retransmission
344 timeouts. It is particularly beneficial in wireless environments
345 where packet loss is typically due to random radio interference
346 rather than intermediate router congestion.
348 tcp_congestion_control - STRING
349 Set the congestion control algorithm to be used for new
350 connections. The algorithm "reno" is always available, but
351 additional choices may be available based on kernel configuration.
353 somaxconn - INTEGER
354 Limit of socket listen() backlog, known in userspace as SOMAXCONN.
355 Defaults to 128. See also tcp_max_syn_backlog for additional tuning
356 for TCP sockets.
358 tcp_workaround_signed_windows - BOOLEAN
359 If set, assume no receipt of a window scaling option means the
360 remote TCP is broken and treats the window as a signed quantity.
361 If unset, assume the remote TCP is not broken even if we do
362 not receive a window scaling option from them.
363 Default: 0
365 tcp_slow_start_after_idle - BOOLEAN
366 If set, provide RFC2861 behavior and time out the congestion
367 window after an idle period. An idle period is defined at
368 the current RTO. If unset, the congestion window will not
369 be timed out after an idle period.
370 Default: 1
372 IP Variables:
374 ip_local_port_range - 2 INTEGERS
375 Defines the local port range that is used by TCP and UDP to
376 choose the local port. The first number is the first, the
377 second the last local port number. Default value depends on
378 amount of memory available on the system:
379 > 128Mb 32768-61000
380 < 128Mb 1024-4999 or even less.
381 This number defines number of active connections, which this
382 system can issue simultaneously to systems not supporting
383 TCP extensions (timestamps). With tcp_tw_recycle enabled
384 (i.e. by default) range 1024-4999 is enough to issue up to
385 2000 connections per second to systems supporting timestamps.
387 ip_nonlocal_bind - BOOLEAN
388 If set, allows processes to bind() to non-local IP addresses,
389 which can be quite useful - but may break some applications.
390 Default: 0
392 ip_dynaddr - BOOLEAN
393 If set non-zero, enables support for dynamic addresses.
394 If set to a non-zero value larger than 1, a kernel log
395 message will be printed when dynamic address rewriting
396 occurs.
397 Default: 0
399 icmp_echo_ignore_all - BOOLEAN
400 If set non-zero, then the kernel will ignore all ICMP ECHO
401 requests sent to it.
402 Default: 0
404 icmp_echo_ignore_broadcasts - BOOLEAN
405 If set non-zero, then the kernel will ignore all ICMP ECHO and
406 TIMESTAMP requests sent to it via broadcast/multicast.
407 Default: 1
409 icmp_ratelimit - INTEGER
410 Limit the maximal rates for sending ICMP packets whose type matches
411 icmp_ratemask (see below) to specific targets.
412 0 to disable any limiting, otherwise the maximal rate in jiffies(1)
413 Default: 100
415 icmp_ratemask - INTEGER
416 Mask made of ICMP types for which rates are being limited.
417 Significant bits: IHGFEDCBA9876543210
418 Default mask: 0000001100000011000 (6168)
420 Bit definitions (see include/linux/icmp.h):
421 0 Echo Reply
422 3 Destination Unreachable *
423 4 Source Quench *
424 5 Redirect
425 8 Echo Request
426 B Time Exceeded *
427 C Parameter Problem *
428 D Timestamp Request
429 E Timestamp Reply
430 F Info Request
431 G Info Reply
432 H Address Mask Request
433 I Address Mask Reply
435 * These are rate limited by default (see default mask above)
437 icmp_ignore_bogus_error_responses - BOOLEAN
438 Some routers violate RFC1122 by sending bogus responses to broadcast
439 frames. Such violations are normally logged via a kernel warning.
440 If this is set to TRUE, the kernel will not give such warnings, which
441 will avoid log file clutter.
442 Default: FALSE
444 icmp_errors_use_inbound_ifaddr - BOOLEAN
446 If zero, icmp error messages are sent with the primary address of
447 the exiting interface.
449 If non-zero, the message will be sent with the primary address of
450 the interface that received the packet that caused the icmp error.
451 This is the behaviour network many administrators will expect from
452 a router. And it can make debugging complicated network layouts
453 much easier.
455 Note that if no primary address exists for the interface selected,
456 then the primary address of the first non-loopback interface that
457 has one will be used regarldess of this setting.
459 Default: 0
461 igmp_max_memberships - INTEGER
462 Change the maximum number of multicast groups we can subscribe to.
463 Default: 20
465 conf/interface/* changes special settings per interface (where "interface" is
466 the name of your network interface)
467 conf/all/* is special, changes the settings for all interfaces
470 log_martians - BOOLEAN
471 Log packets with impossible addresses to kernel log.
472 log_martians for the interface will be enabled if at least one of
473 conf/{all,interface}/log_martians is set to TRUE,
474 it will be disabled otherwise
476 accept_redirects - BOOLEAN
477 Accept ICMP redirect messages.
478 accept_redirects for the interface will be enabled if:
479 - both conf/{all,interface}/accept_redirects are TRUE in the case forwarding
480 for the interface is enabled
481 or
482 - at least one of conf/{all,interface}/accept_redirects is TRUE in the case
483 forwarding for the interface is disabled
484 accept_redirects for the interface will be disabled otherwise
485 default TRUE (host)
486 FALSE (router)
488 forwarding - BOOLEAN
489 Enable IP forwarding on this interface.
491 mc_forwarding - BOOLEAN
492 Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
493 and a multicast routing daemon is required.
494 conf/all/mc_forwarding must also be set to TRUE to enable multicast routing
495 for the interface
497 medium_id - INTEGER
498 Integer value used to differentiate the devices by the medium they
499 are attached to. Two devices can have different id values when
500 the broadcast packets are received only on one of them.
501 The default value 0 means that the device is the only interface
502 to its medium, value of -1 means that medium is not known.
504 Currently, it is used to change the proxy_arp behavior:
505 the proxy_arp feature is enabled for packets forwarded between
506 two devices attached to different media.
508 proxy_arp - BOOLEAN
509 Do proxy arp.
510 proxy_arp for the interface will be enabled if at least one of
511 conf/{all,interface}/proxy_arp is set to TRUE,
512 it will be disabled otherwise
514 shared_media - BOOLEAN
515 Send(router) or accept(host) RFC1620 shared media redirects.
516 Overrides ip_secure_redirects.
517 shared_media for the interface will be enabled if at least one of
518 conf/{all,interface}/shared_media is set to TRUE,
519 it will be disabled otherwise
520 default TRUE
522 secure_redirects - BOOLEAN
523 Accept ICMP redirect messages only for gateways,
524 listed in default gateway list.
525 secure_redirects for the interface will be enabled if at least one of
526 conf/{all,interface}/secure_redirects is set to TRUE,
527 it will be disabled otherwise
528 default TRUE
530 send_redirects - BOOLEAN
531 Send redirects, if router.
532 send_redirects for the interface will be enabled if at least one of
533 conf/{all,interface}/send_redirects is set to TRUE,
534 it will be disabled otherwise
535 Default: TRUE
537 bootp_relay - BOOLEAN
538 Accept packets with source address 0.b.c.d destined
539 not to this host as local ones. It is supposed, that
540 BOOTP relay daemon will catch and forward such packets.
541 conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
542 for the interface
543 default FALSE
544 Not Implemented Yet.
546 accept_source_route - BOOLEAN
547 Accept packets with SRR option.
548 conf/all/accept_source_route must also be set to TRUE to accept packets
549 with SRR option on the interface
550 default TRUE (router)
551 FALSE (host)
553 rp_filter - BOOLEAN
554 1 - do source validation by reversed path, as specified in RFC1812
555 Recommended option for single homed hosts and stub network
556 routers. Could cause troubles for complicated (not loop free)
557 networks running a slow unreliable protocol (sort of RIP),
558 or using static routes.
560 0 - No source validation.
562 conf/all/rp_filter must also be set to TRUE to do source validation
563 on the interface
565 Default value is 0. Note that some distributions enable it
566 in startup scripts.
568 arp_filter - BOOLEAN
569 1 - Allows you to have multiple network interfaces on the same
570 subnet, and have the ARPs for each interface be answered
571 based on whether or not the kernel would route a packet from
572 the ARP'd IP out that interface (therefore you must use source
573 based routing for this to work). In other words it allows control
574 of which cards (usually 1) will respond to an arp request.
576 0 - (default) The kernel can respond to arp requests with addresses
577 from other interfaces. This may seem wrong but it usually makes
578 sense, because it increases the chance of successful communication.
579 IP addresses are owned by the complete host on Linux, not by
580 particular interfaces. Only for more complex setups like load-
581 balancing, does this behaviour cause problems.
583 arp_filter for the interface will be enabled if at least one of
584 conf/{all,interface}/arp_filter is set to TRUE,
585 it will be disabled otherwise
587 arp_announce - INTEGER
588 Define different restriction levels for announcing the local
589 source IP address from IP packets in ARP requests sent on
590 interface:
591 0 - (default) Use any local address, configured on any interface
592 1 - Try to avoid local addresses that are not in the target's
593 subnet for this interface. This mode is useful when target
594 hosts reachable via this interface require the source IP
595 address in ARP requests to be part of their logical network
596 configured on the receiving interface. When we generate the
597 request we will check all our subnets that include the
598 target IP and will preserve the source address if it is from
599 such subnet. If there is no such subnet we select source
600 address according to the rules for level 2.
601 2 - Always use the best local address for this target.
602 In this mode we ignore the source address in the IP packet
603 and try to select local address that we prefer for talks with
604 the target host. Such local address is selected by looking
605 for primary IP addresses on all our subnets on the outgoing
606 interface that include the target IP address. If no suitable
607 local address is found we select the first local address
608 we have on the outgoing interface or on all other interfaces,
609 with the hope we will receive reply for our request and
610 even sometimes no matter the source IP address we announce.
612 The max value from conf/{all,interface}/arp_announce is used.
614 Increasing the restriction level gives more chance for
615 receiving answer from the resolved target while decreasing
616 the level announces more valid sender's information.
618 arp_ignore - INTEGER
619 Define different modes for sending replies in response to
620 received ARP requests that resolve local target IP addresses:
621 0 - (default): reply for any local target IP address, configured
622 on any interface
623 1 - reply only if the target IP address is local address
624 configured on the incoming interface
625 2 - reply only if the target IP address is local address
626 configured on the incoming interface and both with the
627 sender's IP address are part from same subnet on this interface
628 3 - do not reply for local addresses configured with scope host,
629 only resolutions for global and link addresses are replied
630 4-7 - reserved
631 8 - do not reply for all local addresses
633 The max value from conf/{all,interface}/arp_ignore is used
634 when ARP request is received on the {interface}
636 arp_accept - BOOLEAN
637 Define behavior when gratuitous arp replies are received:
638 0 - drop gratuitous arp frames
639 1 - accept gratuitous arp frames
641 app_solicit - INTEGER
642 The maximum number of probes to send to the user space ARP daemon
643 via netlink before dropping back to multicast probes (see
644 mcast_solicit). Defaults to 0.
646 disable_policy - BOOLEAN
647 Disable IPSEC policy (SPD) for this interface
649 disable_xfrm - BOOLEAN
650 Disable IPSEC encryption on this interface, whatever the policy
654 tag - INTEGER
655 Allows you to write a number, which can be used as required.
656 Default value is 0.
658 (1) Jiffie: internal timeunit for the kernel. On the i386 1/100s, on the
659 Alpha 1/1024s. See the HZ define in /usr/include/asm/param.h for the exact
660 value on your system.
662 Alexey Kuznetsov.
663 kuznet@ms2.inr.ac.ru
665 Updated by:
666 Andi Kleen
667 ak@muc.de
668 Nicolas Delon
669 delon.nicolas@wanadoo.fr
674 /proc/sys/net/ipv6/* Variables:
676 IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
677 apply to IPv6 [XXX?].
679 bindv6only - BOOLEAN
680 Default value for IPV6_V6ONLY socket option,
681 which restricts use of the IPv6 socket to IPv6 communication
682 only.
683 TRUE: disable IPv4-mapped address feature
684 FALSE: enable IPv4-mapped address feature
686 Default: FALSE (as specified in RFC2553bis)
688 IPv6 Fragmentation:
690 ip6frag_high_thresh - INTEGER
691 Maximum memory used to reassemble IPv6 fragments. When
692 ip6frag_high_thresh bytes of memory is allocated for this purpose,
693 the fragment handler will toss packets until ip6frag_low_thresh
694 is reached.
696 ip6frag_low_thresh - INTEGER
697 See ip6frag_high_thresh
699 ip6frag_time - INTEGER
700 Time in seconds to keep an IPv6 fragment in memory.
702 ip6frag_secret_interval - INTEGER
703 Regeneration interval (in seconds) of the hash secret (or lifetime
704 for the hash secret) for IPv6 fragments.
705 Default: 600
707 conf/default/*:
708 Change the interface-specific default settings.
711 conf/all/*:
712 Change all the interface-specific settings.
714 [XXX: Other special features than forwarding?]
716 conf/all/forwarding - BOOLEAN
717 Enable global IPv6 forwarding between all interfaces.
719 IPv4 and IPv6 work differently here; e.g. netfilter must be used
720 to control which interfaces may forward packets and which not.
722 This also sets all interfaces' Host/Router setting
723 'forwarding' to the specified value. See below for details.
725 This referred to as global forwarding.
727 conf/interface/*:
728 Change special settings per interface.
730 The functional behaviour for certain settings is different
731 depending on whether local forwarding is enabled or not.
733 accept_ra - BOOLEAN
734 Accept Router Advertisements; autoconfigure using them.
736 Functional default: enabled if local forwarding is disabled.
737 disabled if local forwarding is enabled.
739 accept_ra_defrtr - BOOLEAN
740 Learn default router in Router Advertisement.
742 Functional default: enabled if accept_ra is enabled.
743 disabled if accept_ra is disabled.
745 accept_ra_pinfo - BOOLEAN
746 Learn Prefix Inforamtion in Router Advertisement.
748 Functional default: enabled if accept_ra is enabled.
749 disabled if accept_ra is disabled.
751 accept_ra_rt_info_max_plen - INTEGER
752 Maximum prefix length of Route Information in RA.
754 Route Information w/ prefix larger than or equal to this
755 variable shall be ignored.
757 Functional default: 0 if accept_ra_rtr_pref is enabled.
758 -1 if accept_ra_rtr_pref is disabled.
760 accept_ra_rtr_pref - BOOLEAN
761 Accept Router Preference in RA.
763 Functional default: enabled if accept_ra is enabled.
764 disabled if accept_ra is disabled.
766 accept_redirects - BOOLEAN
767 Accept Redirects.
769 Functional default: enabled if local forwarding is disabled.
770 disabled if local forwarding is enabled.
772 autoconf - BOOLEAN
773 Autoconfigure addresses using Prefix Information in Router
774 Advertisements.
776 Functional default: enabled if accept_ra_pinfo is enabled.
777 disabled if accept_ra_pinfo is disabled.
779 dad_transmits - INTEGER
780 The amount of Duplicate Address Detection probes to send.
781 Default: 1
783 forwarding - BOOLEAN
784 Configure interface-specific Host/Router behaviour.
786 Note: It is recommended to have the same setting on all
787 interfaces; mixed router/host scenarios are rather uncommon.
789 FALSE:
791 By default, Host behaviour is assumed. This means:
793 1. IsRouter flag is not set in Neighbour Advertisements.
794 2. Router Solicitations are being sent when necessary.
795 3. If accept_ra is TRUE (default), accept Router
796 Advertisements (and do autoconfiguration).
797 4. If accept_redirects is TRUE (default), accept Redirects.
799 TRUE:
801 If local forwarding is enabled, Router behaviour is assumed.
802 This means exactly the reverse from the above:
804 1. IsRouter flag is set in Neighbour Advertisements.
805 2. Router Solicitations are not sent.
806 3. Router Advertisements are ignored.
807 4. Redirects are ignored.
809 Default: FALSE if global forwarding is disabled (default),
810 otherwise TRUE.
812 hop_limit - INTEGER
813 Default Hop Limit to set.
814 Default: 64
816 mtu - INTEGER
817 Default Maximum Transfer Unit
818 Default: 1280 (IPv6 required minimum)
820 router_probe_interval - INTEGER
821 Minimum interval (in seconds) between Router Probing described
822 in RFC4191.
824 Default: 60
826 router_solicitation_delay - INTEGER
827 Number of seconds to wait after interface is brought up
828 before sending Router Solicitations.
829 Default: 1
831 router_solicitation_interval - INTEGER
832 Number of seconds to wait between Router Solicitations.
833 Default: 4
835 router_solicitations - INTEGER
836 Number of Router Solicitations to send until assuming no
837 routers are present.
838 Default: 3
840 use_tempaddr - INTEGER
841 Preference for Privacy Extensions (RFC3041).
842 <= 0 : disable Privacy Extensions
843 == 1 : enable Privacy Extensions, but prefer public
844 addresses over temporary addresses.
845 > 1 : enable Privacy Extensions and prefer temporary
846 addresses over public addresses.
847 Default: 0 (for most devices)
848 -1 (for point-to-point devices and loopback devices)
850 temp_valid_lft - INTEGER
851 valid lifetime (in seconds) for temporary addresses.
852 Default: 604800 (7 days)
854 temp_prefered_lft - INTEGER
855 Preferred lifetime (in seconds) for temporary addresses.
856 Default: 86400 (1 day)
858 max_desync_factor - INTEGER
859 Maximum value for DESYNC_FACTOR, which is a random value
860 that ensures that clients don't synchronize with each
861 other and generate new addresses at exactly the same time.
862 value is in seconds.
863 Default: 600
865 regen_max_retry - INTEGER
866 Number of attempts before give up attempting to generate
867 valid temporary addresses.
868 Default: 5
870 max_addresses - INTEGER
871 Number of maximum addresses per interface. 0 disables limitation.
872 It is recommended not set too large value (or 0) because it would
873 be too easy way to crash kernel to allow to create too much of
874 autoconfigured addresses.
875 Default: 16
877 icmp/*:
878 ratelimit - INTEGER
879 Limit the maximal rates for sending ICMPv6 packets.
880 0 to disable any limiting, otherwise the maximal rate in jiffies(1)
881 Default: 100
884 IPv6 Update by:
885 Pekka Savola <pekkas@netcore.fi>
886 YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
889 /proc/sys/net/bridge/* Variables:
891 bridge-nf-call-arptables - BOOLEAN
892 1 : pass bridged ARP traffic to arptables' FORWARD chain.
893 0 : disable this.
894 Default: 1
896 bridge-nf-call-iptables - BOOLEAN
897 1 : pass bridged IPv4 traffic to iptables' chains.
898 0 : disable this.
899 Default: 1
901 bridge-nf-call-ip6tables - BOOLEAN
902 1 : pass bridged IPv6 traffic to ip6tables' chains.
903 0 : disable this.
904 Default: 1
906 bridge-nf-filter-vlan-tagged - BOOLEAN
907 1 : pass bridged vlan-tagged ARP/IP traffic to arptables/iptables.
908 0 : disable this.
909 Default: 1
912 UNDOCUMENTED:
914 dev_weight FIXME
915 discovery_slots FIXME
916 discovery_timeout FIXME
917 fast_poll_increase FIXME
918 ip6_queue_maxlen FIXME
919 lap_keepalive_time FIXME
920 lo_cong FIXME
921 max_baud_rate FIXME
922 max_dgram_qlen FIXME
923 max_noreply_time FIXME
924 max_tx_data_size FIXME
925 max_tx_window FIXME
926 min_tx_turn_time FIXME
927 mod_cong FIXME
928 no_cong FIXME
929 no_cong_thresh FIXME
930 slot_timeout FIXME
931 warn_noreply_time FIXME
933 $Id: ip-sysctl.txt,v 1.20 2001/12/13 09:00:18 davem Exp $