ip-sysctl.txt 30 KB

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  1. /proc/sys/net/ipv4/* Variables:
  2. ip_forward - BOOLEAN
  3. 0 - disabled (default)
  4. not 0 - enabled
  5. Forward Packets between interfaces.
  6. This variable is special, its change resets all configuration
  7. parameters to their default state (RFC1122 for hosts, RFC1812
  8. for routers)
  9. ip_default_ttl - INTEGER
  10. default 64
  11. ip_no_pmtu_disc - BOOLEAN
  12. Disable Path MTU Discovery.
  13. default FALSE
  14. min_pmtu - INTEGER
  15. default 562 - minimum discovered Path MTU
  16. mtu_expires - INTEGER
  17. Time, in seconds, that cached PMTU information is kept.
  18. min_adv_mss - INTEGER
  19. The advertised MSS depends on the first hop route MTU, but will
  20. never be lower than this setting.
  21. IP Fragmentation:
  22. ipfrag_high_thresh - INTEGER
  23. Maximum memory used to reassemble IP fragments. When
  24. ipfrag_high_thresh bytes of memory is allocated for this purpose,
  25. the fragment handler will toss packets until ipfrag_low_thresh
  26. is reached.
  27. ipfrag_low_thresh - INTEGER
  28. See ipfrag_high_thresh
  29. ipfrag_time - INTEGER
  30. Time in seconds to keep an IP fragment in memory.
  31. ipfrag_secret_interval - INTEGER
  32. Regeneration interval (in seconds) of the hash secret (or lifetime
  33. for the hash secret) for IP fragments.
  34. Default: 600
  35. ipfrag_max_dist - INTEGER
  36. ipfrag_max_dist is a non-negative integer value which defines the
  37. maximum "disorder" which is allowed among fragments which share a
  38. common IP source address. Note that reordering of packets is
  39. not unusual, but if a large number of fragments arrive from a source
  40. IP address while a particular fragment queue remains incomplete, it
  41. probably indicates that one or more fragments belonging to that queue
  42. have been lost. When ipfrag_max_dist is positive, an additional check
  43. is done on fragments before they are added to a reassembly queue - if
  44. ipfrag_max_dist (or more) fragments have arrived from a particular IP
  45. address between additions to any IP fragment queue using that source
  46. address, it's presumed that one or more fragments in the queue are
  47. lost. The existing fragment queue will be dropped, and a new one
  48. started. An ipfrag_max_dist value of zero disables this check.
  49. Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
  50. result in unnecessarily dropping fragment queues when normal
  51. reordering of packets occurs, which could lead to poor application
  52. performance. Using a very large value, e.g. 50000, increases the
  53. likelihood of incorrectly reassembling IP fragments that originate
  54. from different IP datagrams, which could result in data corruption.
  55. Default: 64
  56. INET peer storage:
  57. inet_peer_threshold - INTEGER
  58. The approximate size of the storage. Starting from this threshold
  59. entries will be thrown aggressively. This threshold also determines
  60. entries' time-to-live and time intervals between garbage collection
  61. passes. More entries, less time-to-live, less GC interval.
  62. inet_peer_minttl - INTEGER
  63. Minimum time-to-live of entries. Should be enough to cover fragment
  64. time-to-live on the reassembling side. This minimum time-to-live is
  65. guaranteed if the pool size is less than inet_peer_threshold.
  66. Measured in jiffies(1).
  67. inet_peer_maxttl - INTEGER
  68. Maximum time-to-live of entries. Unused entries will expire after
  69. this period of time if there is no memory pressure on the pool (i.e.
  70. when the number of entries in the pool is very small).
  71. Measured in jiffies(1).
  72. inet_peer_gc_mintime - INTEGER
  73. Minimum interval between garbage collection passes. This interval is
  74. in effect under high memory pressure on the pool.
  75. Measured in jiffies(1).
  76. inet_peer_gc_maxtime - INTEGER
  77. Minimum interval between garbage collection passes. This interval is
  78. in effect under low (or absent) memory pressure on the pool.
  79. Measured in jiffies(1).
  80. TCP variables:
  81. tcp_abc - INTEGER
  82. Controls Appropriate Byte Count defined in RFC3465. If set to
  83. 0 then does congestion avoid once per ack. 1 is conservative
  84. value, and 2 is more agressive.
  85. tcp_syn_retries - INTEGER
  86. Number of times initial SYNs for an active TCP connection attempt
  87. will be retransmitted. Should not be higher than 255. Default value
  88. is 5, which corresponds to ~180seconds.
  89. tcp_synack_retries - INTEGER
  90. Number of times SYNACKs for a passive TCP connection attempt will
  91. be retransmitted. Should not be higher than 255. Default value
  92. is 5, which corresponds to ~180seconds.
  93. tcp_keepalive_time - INTEGER
  94. How often TCP sends out keepalive messages when keepalive is enabled.
  95. Default: 2hours.
  96. tcp_keepalive_probes - INTEGER
  97. How many keepalive probes TCP sends out, until it decides that the
  98. connection is broken. Default value: 9.
  99. tcp_keepalive_intvl - INTEGER
  100. How frequently the probes are send out. Multiplied by
  101. tcp_keepalive_probes it is time to kill not responding connection,
  102. after probes started. Default value: 75sec i.e. connection
  103. will be aborted after ~11 minutes of retries.
  104. tcp_retries1 - INTEGER
  105. How many times to retry before deciding that something is wrong
  106. and it is necessary to report this suspicion to network layer.
  107. Minimal RFC value is 3, it is default, which corresponds
  108. to ~3sec-8min depending on RTO.
  109. tcp_retries2 - INTEGER
  110. How may times to retry before killing alive TCP connection.
  111. RFC1122 says that the limit should be longer than 100 sec.
  112. It is too small number. Default value 15 corresponds to ~13-30min
  113. depending on RTO.
  114. tcp_orphan_retries - INTEGER
  115. How may times to retry before killing TCP connection, closed
  116. by our side. Default value 7 corresponds to ~50sec-16min
  117. depending on RTO. If you machine is loaded WEB server,
  118. you should think about lowering this value, such sockets
  119. may consume significant resources. Cf. tcp_max_orphans.
  120. tcp_fin_timeout - INTEGER
  121. Time to hold socket in state FIN-WAIT-2, if it was closed
  122. by our side. Peer can be broken and never close its side,
  123. or even died unexpectedly. Default value is 60sec.
  124. Usual value used in 2.2 was 180 seconds, you may restore
  125. it, but remember that if your machine is even underloaded WEB server,
  126. you risk to overflow memory with kilotons of dead sockets,
  127. FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1,
  128. because they eat maximum 1.5K of memory, but they tend
  129. to live longer. Cf. tcp_max_orphans.
  130. tcp_max_tw_buckets - INTEGER
  131. Maximal number of timewait sockets held by system simultaneously.
  132. If this number is exceeded time-wait socket is immediately destroyed
  133. and warning is printed. This limit exists only to prevent
  134. simple DoS attacks, you _must_ not lower the limit artificially,
  135. but rather increase it (probably, after increasing installed memory),
  136. if network conditions require more than default value.
  137. tcp_tw_recycle - BOOLEAN
  138. Enable fast recycling TIME-WAIT sockets. Default value is 0.
  139. It should not be changed without advice/request of technical
  140. experts.
  141. tcp_tw_reuse - BOOLEAN
  142. Allow to reuse TIME-WAIT sockets for new connections when it is
  143. safe from protocol viewpoint. Default value is 0.
  144. It should not be changed without advice/request of technical
  145. experts.
  146. tcp_max_orphans - INTEGER
  147. Maximal number of TCP sockets not attached to any user file handle,
  148. held by system. If this number is exceeded orphaned connections are
  149. reset immediately and warning is printed. This limit exists
  150. only to prevent simple DoS attacks, you _must_ not rely on this
  151. or lower the limit artificially, but rather increase it
  152. (probably, after increasing installed memory),
  153. if network conditions require more than default value,
  154. and tune network services to linger and kill such states
  155. more aggressively. Let me to remind again: each orphan eats
  156. up to ~64K of unswappable memory.
  157. tcp_abort_on_overflow - BOOLEAN
  158. If listening service is too slow to accept new connections,
  159. reset them. Default state is FALSE. It means that if overflow
  160. occurred due to a burst, connection will recover. Enable this
  161. option _only_ if you are really sure that listening daemon
  162. cannot be tuned to accept connections faster. Enabling this
  163. option can harm clients of your server.
  164. tcp_syncookies - BOOLEAN
  165. Only valid when the kernel was compiled with CONFIG_SYNCOOKIES
  166. Send out syncookies when the syn backlog queue of a socket
  167. overflows. This is to prevent against the common 'syn flood attack'
  168. Default: FALSE
  169. Note, that syncookies is fallback facility.
  170. It MUST NOT be used to help highly loaded servers to stand
  171. against legal connection rate. If you see synflood warnings
  172. in your logs, but investigation shows that they occur
  173. because of overload with legal connections, you should tune
  174. another parameters until this warning disappear.
  175. See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
  176. syncookies seriously violate TCP protocol, do not allow
  177. to use TCP extensions, can result in serious degradation
  178. of some services (f.e. SMTP relaying), visible not by you,
  179. but your clients and relays, contacting you. While you see
  180. synflood warnings in logs not being really flooded, your server
  181. is seriously misconfigured.
  182. tcp_stdurg - BOOLEAN
  183. Use the Host requirements interpretation of the TCP urg pointer field.
  184. Most hosts use the older BSD interpretation, so if you turn this on
  185. Linux might not communicate correctly with them.
  186. Default: FALSE
  187. tcp_max_syn_backlog - INTEGER
  188. Maximal number of remembered connection requests, which are
  189. still did not receive an acknowledgment from connecting client.
  190. Default value is 1024 for systems with more than 128Mb of memory,
  191. and 128 for low memory machines. If server suffers of overload,
  192. try to increase this number.
  193. tcp_window_scaling - BOOLEAN
  194. Enable window scaling as defined in RFC1323.
  195. tcp_timestamps - BOOLEAN
  196. Enable timestamps as defined in RFC1323.
  197. tcp_sack - BOOLEAN
  198. Enable select acknowledgments (SACKS).
  199. tcp_fack - BOOLEAN
  200. Enable FACK congestion avoidance and fast retransmission.
  201. The value is not used, if tcp_sack is not enabled.
  202. tcp_dsack - BOOLEAN
  203. Allows TCP to send "duplicate" SACKs.
  204. tcp_ecn - BOOLEAN
  205. Enable Explicit Congestion Notification in TCP.
  206. tcp_reordering - INTEGER
  207. Maximal reordering of packets in a TCP stream.
  208. Default: 3
  209. tcp_retrans_collapse - BOOLEAN
  210. Bug-to-bug compatibility with some broken printers.
  211. On retransmit try to send bigger packets to work around bugs in
  212. certain TCP stacks.
  213. tcp_wmem - vector of 3 INTEGERs: min, default, max
  214. min: Amount of memory reserved for send buffers for TCP socket.
  215. Each TCP socket has rights to use it due to fact of its birth.
  216. Default: 4K
  217. default: Amount of memory allowed for send buffers for TCP socket
  218. by default. This value overrides net.core.wmem_default used
  219. by other protocols, it is usually lower than net.core.wmem_default.
  220. Default: 16K
  221. max: Maximal amount of memory allowed for automatically selected
  222. send buffers for TCP socket. This value does not override
  223. net.core.wmem_max, "static" selection via SO_SNDBUF does not use this.
  224. Default: 128K
  225. tcp_rmem - vector of 3 INTEGERs: min, default, max
  226. min: Minimal size of receive buffer used by TCP sockets.
  227. It is guaranteed to each TCP socket, even under moderate memory
  228. pressure.
  229. Default: 8K
  230. default: default size of receive buffer used by TCP sockets.
  231. This value overrides net.core.rmem_default used by other protocols.
  232. Default: 87380 bytes. This value results in window of 65535 with
  233. default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
  234. less for default tcp_app_win. See below about these variables.
  235. max: maximal size of receive buffer allowed for automatically
  236. selected receiver buffers for TCP socket. This value does not override
  237. net.core.rmem_max, "static" selection via SO_RCVBUF does not use this.
  238. Default: 87380*2 bytes.
  239. tcp_mem - vector of 3 INTEGERs: min, pressure, max
  240. low: below this number of pages TCP is not bothered about its
  241. memory appetite.
  242. pressure: when amount of memory allocated by TCP exceeds this number
  243. of pages, TCP moderates its memory consumption and enters memory
  244. pressure mode, which is exited when memory consumption falls
  245. under "low".
  246. high: number of pages allowed for queueing by all TCP sockets.
  247. Defaults are calculated at boot time from amount of available
  248. memory.
  249. tcp_app_win - INTEGER
  250. Reserve max(window/2^tcp_app_win, mss) of window for application
  251. buffer. Value 0 is special, it means that nothing is reserved.
  252. Default: 31
  253. tcp_adv_win_scale - INTEGER
  254. Count buffering overhead as bytes/2^tcp_adv_win_scale
  255. (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
  256. if it is <= 0.
  257. Default: 2
  258. tcp_rfc1337 - BOOLEAN
  259. If set, the TCP stack behaves conforming to RFC1337. If unset,
  260. we are not conforming to RFC, but prevent TCP TIME_WAIT
  261. assassination.
  262. Default: 0
  263. tcp_low_latency - BOOLEAN
  264. If set, the TCP stack makes decisions that prefer lower
  265. latency as opposed to higher throughput. By default, this
  266. option is not set meaning that higher throughput is preferred.
  267. An example of an application where this default should be
  268. changed would be a Beowulf compute cluster.
  269. Default: 0
  270. tcp_tso_win_divisor - INTEGER
  271. This allows control over what percentage of the congestion window
  272. can be consumed by a single TSO frame.
  273. The setting of this parameter is a choice between burstiness and
  274. building larger TSO frames.
  275. Default: 3
  276. tcp_frto - BOOLEAN
  277. Enables F-RTO, an enhanced recovery algorithm for TCP retransmission
  278. timeouts. It is particularly beneficial in wireless environments
  279. where packet loss is typically due to random radio interference
  280. rather than intermediate router congestion.
  281. tcp_congestion_control - STRING
  282. Set the congestion control algorithm to be used for new
  283. connections. The algorithm "reno" is always available, but
  284. additional choices may be available based on kernel configuration.
  285. somaxconn - INTEGER
  286. Limit of socket listen() backlog, known in userspace as SOMAXCONN.
  287. Defaults to 128. See also tcp_max_syn_backlog for additional tuning
  288. for TCP sockets.
  289. IP Variables:
  290. ip_local_port_range - 2 INTEGERS
  291. Defines the local port range that is used by TCP and UDP to
  292. choose the local port. The first number is the first, the
  293. second the last local port number. Default value depends on
  294. amount of memory available on the system:
  295. > 128Mb 32768-61000
  296. < 128Mb 1024-4999 or even less.
  297. This number defines number of active connections, which this
  298. system can issue simultaneously to systems not supporting
  299. TCP extensions (timestamps). With tcp_tw_recycle enabled
  300. (i.e. by default) range 1024-4999 is enough to issue up to
  301. 2000 connections per second to systems supporting timestamps.
  302. ip_nonlocal_bind - BOOLEAN
  303. If set, allows processes to bind() to non-local IP addresses,
  304. which can be quite useful - but may break some applications.
  305. Default: 0
  306. ip_dynaddr - BOOLEAN
  307. If set non-zero, enables support for dynamic addresses.
  308. If set to a non-zero value larger than 1, a kernel log
  309. message will be printed when dynamic address rewriting
  310. occurs.
  311. Default: 0
  312. icmp_echo_ignore_all - BOOLEAN
  313. If set non-zero, then the kernel will ignore all ICMP ECHO
  314. requests sent to it.
  315. Default: 0
  316. icmp_echo_ignore_broadcasts - BOOLEAN
  317. If set non-zero, then the kernel will ignore all ICMP ECHO and
  318. TIMESTAMP requests sent to it via broadcast/multicast.
  319. Default: 1
  320. icmp_ratelimit - INTEGER
  321. Limit the maximal rates for sending ICMP packets whose type matches
  322. icmp_ratemask (see below) to specific targets.
  323. 0 to disable any limiting, otherwise the maximal rate in jiffies(1)
  324. Default: 100
  325. icmp_ratemask - INTEGER
  326. Mask made of ICMP types for which rates are being limited.
  327. Significant bits: IHGFEDCBA9876543210
  328. Default mask: 0000001100000011000 (6168)
  329. Bit definitions (see include/linux/icmp.h):
  330. 0 Echo Reply
  331. 3 Destination Unreachable *
  332. 4 Source Quench *
  333. 5 Redirect
  334. 8 Echo Request
  335. B Time Exceeded *
  336. C Parameter Problem *
  337. D Timestamp Request
  338. E Timestamp Reply
  339. F Info Request
  340. G Info Reply
  341. H Address Mask Request
  342. I Address Mask Reply
  343. * These are rate limited by default (see default mask above)
  344. icmp_ignore_bogus_error_responses - BOOLEAN
  345. Some routers violate RFC1122 by sending bogus responses to broadcast
  346. frames. Such violations are normally logged via a kernel warning.
  347. If this is set to TRUE, the kernel will not give such warnings, which
  348. will avoid log file clutter.
  349. Default: FALSE
  350. icmp_errors_use_inbound_ifaddr - BOOLEAN
  351. If zero, icmp error messages are sent with the primary address of
  352. the exiting interface.
  353. If non-zero, the message will be sent with the primary address of
  354. the interface that received the packet that caused the icmp error.
  355. This is the behaviour network many administrators will expect from
  356. a router. And it can make debugging complicated network layouts
  357. much easier.
  358. Note that if no primary address exists for the interface selected,
  359. then the primary address of the first non-loopback interface that
  360. has one will be used regarldess of this setting.
  361. Default: 0
  362. igmp_max_memberships - INTEGER
  363. Change the maximum number of multicast groups we can subscribe to.
  364. Default: 20
  365. conf/interface/* changes special settings per interface (where "interface" is
  366. the name of your network interface)
  367. conf/all/* is special, changes the settings for all interfaces
  368. log_martians - BOOLEAN
  369. Log packets with impossible addresses to kernel log.
  370. log_martians for the interface will be enabled if at least one of
  371. conf/{all,interface}/log_martians is set to TRUE,
  372. it will be disabled otherwise
  373. accept_redirects - BOOLEAN
  374. Accept ICMP redirect messages.
  375. accept_redirects for the interface will be enabled if:
  376. - both conf/{all,interface}/accept_redirects are TRUE in the case forwarding
  377. for the interface is enabled
  378. or
  379. - at least one of conf/{all,interface}/accept_redirects is TRUE in the case
  380. forwarding for the interface is disabled
  381. accept_redirects for the interface will be disabled otherwise
  382. default TRUE (host)
  383. FALSE (router)
  384. forwarding - BOOLEAN
  385. Enable IP forwarding on this interface.
  386. mc_forwarding - BOOLEAN
  387. Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
  388. and a multicast routing daemon is required.
  389. conf/all/mc_forwarding must also be set to TRUE to enable multicast routing
  390. for the interface
  391. medium_id - INTEGER
  392. Integer value used to differentiate the devices by the medium they
  393. are attached to. Two devices can have different id values when
  394. the broadcast packets are received only on one of them.
  395. The default value 0 means that the device is the only interface
  396. to its medium, value of -1 means that medium is not known.
  397. Currently, it is used to change the proxy_arp behavior:
  398. the proxy_arp feature is enabled for packets forwarded between
  399. two devices attached to different media.
  400. proxy_arp - BOOLEAN
  401. Do proxy arp.
  402. proxy_arp for the interface will be enabled if at least one of
  403. conf/{all,interface}/proxy_arp is set to TRUE,
  404. it will be disabled otherwise
  405. shared_media - BOOLEAN
  406. Send(router) or accept(host) RFC1620 shared media redirects.
  407. Overrides ip_secure_redirects.
  408. shared_media for the interface will be enabled if at least one of
  409. conf/{all,interface}/shared_media is set to TRUE,
  410. it will be disabled otherwise
  411. default TRUE
  412. secure_redirects - BOOLEAN
  413. Accept ICMP redirect messages only for gateways,
  414. listed in default gateway list.
  415. secure_redirects for the interface will be enabled if at least one of
  416. conf/{all,interface}/secure_redirects is set to TRUE,
  417. it will be disabled otherwise
  418. default TRUE
  419. send_redirects - BOOLEAN
  420. Send redirects, if router.
  421. send_redirects for the interface will be enabled if at least one of
  422. conf/{all,interface}/send_redirects is set to TRUE,
  423. it will be disabled otherwise
  424. Default: TRUE
  425. bootp_relay - BOOLEAN
  426. Accept packets with source address 0.b.c.d destined
  427. not to this host as local ones. It is supposed, that
  428. BOOTP relay daemon will catch and forward such packets.
  429. conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
  430. for the interface
  431. default FALSE
  432. Not Implemented Yet.
  433. accept_source_route - BOOLEAN
  434. Accept packets with SRR option.
  435. conf/all/accept_source_route must also be set to TRUE to accept packets
  436. with SRR option on the interface
  437. default TRUE (router)
  438. FALSE (host)
  439. rp_filter - BOOLEAN
  440. 1 - do source validation by reversed path, as specified in RFC1812
  441. Recommended option for single homed hosts and stub network
  442. routers. Could cause troubles for complicated (not loop free)
  443. networks running a slow unreliable protocol (sort of RIP),
  444. or using static routes.
  445. 0 - No source validation.
  446. conf/all/rp_filter must also be set to TRUE to do source validation
  447. on the interface
  448. Default value is 0. Note that some distributions enable it
  449. in startup scripts.
  450. arp_filter - BOOLEAN
  451. 1 - Allows you to have multiple network interfaces on the same
  452. subnet, and have the ARPs for each interface be answered
  453. based on whether or not the kernel would route a packet from
  454. the ARP'd IP out that interface (therefore you must use source
  455. based routing for this to work). In other words it allows control
  456. of which cards (usually 1) will respond to an arp request.
  457. 0 - (default) The kernel can respond to arp requests with addresses
  458. from other interfaces. This may seem wrong but it usually makes
  459. sense, because it increases the chance of successful communication.
  460. IP addresses are owned by the complete host on Linux, not by
  461. particular interfaces. Only for more complex setups like load-
  462. balancing, does this behaviour cause problems.
  463. arp_filter for the interface will be enabled if at least one of
  464. conf/{all,interface}/arp_filter is set to TRUE,
  465. it will be disabled otherwise
  466. arp_announce - INTEGER
  467. Define different restriction levels for announcing the local
  468. source IP address from IP packets in ARP requests sent on
  469. interface:
  470. 0 - (default) Use any local address, configured on any interface
  471. 1 - Try to avoid local addresses that are not in the target's
  472. subnet for this interface. This mode is useful when target
  473. hosts reachable via this interface require the source IP
  474. address in ARP requests to be part of their logical network
  475. configured on the receiving interface. When we generate the
  476. request we will check all our subnets that include the
  477. target IP and will preserve the source address if it is from
  478. such subnet. If there is no such subnet we select source
  479. address according to the rules for level 2.
  480. 2 - Always use the best local address for this target.
  481. In this mode we ignore the source address in the IP packet
  482. and try to select local address that we prefer for talks with
  483. the target host. Such local address is selected by looking
  484. for primary IP addresses on all our subnets on the outgoing
  485. interface that include the target IP address. If no suitable
  486. local address is found we select the first local address
  487. we have on the outgoing interface or on all other interfaces,
  488. with the hope we will receive reply for our request and
  489. even sometimes no matter the source IP address we announce.
  490. The max value from conf/{all,interface}/arp_announce is used.
  491. Increasing the restriction level gives more chance for
  492. receiving answer from the resolved target while decreasing
  493. the level announces more valid sender's information.
  494. arp_ignore - INTEGER
  495. Define different modes for sending replies in response to
  496. received ARP requests that resolve local target IP addresses:
  497. 0 - (default): reply for any local target IP address, configured
  498. on any interface
  499. 1 - reply only if the target IP address is local address
  500. configured on the incoming interface
  501. 2 - reply only if the target IP address is local address
  502. configured on the incoming interface and both with the
  503. sender's IP address are part from same subnet on this interface
  504. 3 - do not reply for local addresses configured with scope host,
  505. only resolutions for global and link addresses are replied
  506. 4-7 - reserved
  507. 8 - do not reply for all local addresses
  508. The max value from conf/{all,interface}/arp_ignore is used
  509. when ARP request is received on the {interface}
  510. app_solicit - INTEGER
  511. The maximum number of probes to send to the user space ARP daemon
  512. via netlink before dropping back to multicast probes (see
  513. mcast_solicit). Defaults to 0.
  514. disable_policy - BOOLEAN
  515. Disable IPSEC policy (SPD) for this interface
  516. disable_xfrm - BOOLEAN
  517. Disable IPSEC encryption on this interface, whatever the policy
  518. tag - INTEGER
  519. Allows you to write a number, which can be used as required.
  520. Default value is 0.
  521. (1) Jiffie: internal timeunit for the kernel. On the i386 1/100s, on the
  522. Alpha 1/1024s. See the HZ define in /usr/include/asm/param.h for the exact
  523. value on your system.
  524. Alexey Kuznetsov.
  525. kuznet@ms2.inr.ac.ru
  526. Updated by:
  527. Andi Kleen
  528. ak@muc.de
  529. Nicolas Delon
  530. delon.nicolas@wanadoo.fr
  531. /proc/sys/net/ipv6/* Variables:
  532. IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
  533. apply to IPv6 [XXX?].
  534. bindv6only - BOOLEAN
  535. Default value for IPV6_V6ONLY socket option,
  536. which restricts use of the IPv6 socket to IPv6 communication
  537. only.
  538. TRUE: disable IPv4-mapped address feature
  539. FALSE: enable IPv4-mapped address feature
  540. Default: FALSE (as specified in RFC2553bis)
  541. IPv6 Fragmentation:
  542. ip6frag_high_thresh - INTEGER
  543. Maximum memory used to reassemble IPv6 fragments. When
  544. ip6frag_high_thresh bytes of memory is allocated for this purpose,
  545. the fragment handler will toss packets until ip6frag_low_thresh
  546. is reached.
  547. ip6frag_low_thresh - INTEGER
  548. See ip6frag_high_thresh
  549. ip6frag_time - INTEGER
  550. Time in seconds to keep an IPv6 fragment in memory.
  551. ip6frag_secret_interval - INTEGER
  552. Regeneration interval (in seconds) of the hash secret (or lifetime
  553. for the hash secret) for IPv6 fragments.
  554. Default: 600
  555. conf/default/*:
  556. Change the interface-specific default settings.
  557. conf/all/*:
  558. Change all the interface-specific settings.
  559. [XXX: Other special features than forwarding?]
  560. conf/all/forwarding - BOOLEAN
  561. Enable global IPv6 forwarding between all interfaces.
  562. IPv4 and IPv6 work differently here; e.g. netfilter must be used
  563. to control which interfaces may forward packets and which not.
  564. This also sets all interfaces' Host/Router setting
  565. 'forwarding' to the specified value. See below for details.
  566. This referred to as global forwarding.
  567. conf/interface/*:
  568. Change special settings per interface.
  569. The functional behaviour for certain settings is different
  570. depending on whether local forwarding is enabled or not.
  571. accept_ra - BOOLEAN
  572. Accept Router Advertisements; autoconfigure using them.
  573. Functional default: enabled if local forwarding is disabled.
  574. disabled if local forwarding is enabled.
  575. accept_redirects - BOOLEAN
  576. Accept Redirects.
  577. Functional default: enabled if local forwarding is disabled.
  578. disabled if local forwarding is enabled.
  579. autoconf - BOOLEAN
  580. Autoconfigure addresses using Prefix Information in Router
  581. Advertisements.
  582. Functional default: enabled if accept_ra is enabled.
  583. disabled if accept_ra is disabled.
  584. dad_transmits - INTEGER
  585. The amount of Duplicate Address Detection probes to send.
  586. Default: 1
  587. forwarding - BOOLEAN
  588. Configure interface-specific Host/Router behaviour.
  589. Note: It is recommended to have the same setting on all
  590. interfaces; mixed router/host scenarios are rather uncommon.
  591. FALSE:
  592. By default, Host behaviour is assumed. This means:
  593. 1. IsRouter flag is not set in Neighbour Advertisements.
  594. 2. Router Solicitations are being sent when necessary.
  595. 3. If accept_ra is TRUE (default), accept Router
  596. Advertisements (and do autoconfiguration).
  597. 4. If accept_redirects is TRUE (default), accept Redirects.
  598. TRUE:
  599. If local forwarding is enabled, Router behaviour is assumed.
  600. This means exactly the reverse from the above:
  601. 1. IsRouter flag is set in Neighbour Advertisements.
  602. 2. Router Solicitations are not sent.
  603. 3. Router Advertisements are ignored.
  604. 4. Redirects are ignored.
  605. Default: FALSE if global forwarding is disabled (default),
  606. otherwise TRUE.
  607. hop_limit - INTEGER
  608. Default Hop Limit to set.
  609. Default: 64
  610. mtu - INTEGER
  611. Default Maximum Transfer Unit
  612. Default: 1280 (IPv6 required minimum)
  613. router_solicitation_delay - INTEGER
  614. Number of seconds to wait after interface is brought up
  615. before sending Router Solicitations.
  616. Default: 1
  617. router_solicitation_interval - INTEGER
  618. Number of seconds to wait between Router Solicitations.
  619. Default: 4
  620. router_solicitations - INTEGER
  621. Number of Router Solicitations to send until assuming no
  622. routers are present.
  623. Default: 3
  624. use_tempaddr - INTEGER
  625. Preference for Privacy Extensions (RFC3041).
  626. <= 0 : disable Privacy Extensions
  627. == 1 : enable Privacy Extensions, but prefer public
  628. addresses over temporary addresses.
  629. > 1 : enable Privacy Extensions and prefer temporary
  630. addresses over public addresses.
  631. Default: 0 (for most devices)
  632. -1 (for point-to-point devices and loopback devices)
  633. temp_valid_lft - INTEGER
  634. valid lifetime (in seconds) for temporary addresses.
  635. Default: 604800 (7 days)
  636. temp_prefered_lft - INTEGER
  637. Preferred lifetime (in seconds) for temporary addresses.
  638. Default: 86400 (1 day)
  639. max_desync_factor - INTEGER
  640. Maximum value for DESYNC_FACTOR, which is a random value
  641. that ensures that clients don't synchronize with each
  642. other and generate new addresses at exactly the same time.
  643. value is in seconds.
  644. Default: 600
  645. regen_max_retry - INTEGER
  646. Number of attempts before give up attempting to generate
  647. valid temporary addresses.
  648. Default: 5
  649. max_addresses - INTEGER
  650. Number of maximum addresses per interface. 0 disables limitation.
  651. It is recommended not set too large value (or 0) because it would
  652. be too easy way to crash kernel to allow to create too much of
  653. autoconfigured addresses.
  654. Default: 16
  655. icmp/*:
  656. ratelimit - INTEGER
  657. Limit the maximal rates for sending ICMPv6 packets.
  658. 0 to disable any limiting, otherwise the maximal rate in jiffies(1)
  659. Default: 100
  660. IPv6 Update by:
  661. Pekka Savola <pekkas@netcore.fi>
  662. YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
  663. /proc/sys/net/bridge/* Variables:
  664. bridge-nf-call-arptables - BOOLEAN
  665. 1 : pass bridged ARP traffic to arptables' FORWARD chain.
  666. 0 : disable this.
  667. Default: 1
  668. bridge-nf-call-iptables - BOOLEAN
  669. 1 : pass bridged IPv4 traffic to iptables' chains.
  670. 0 : disable this.
  671. Default: 1
  672. bridge-nf-call-ip6tables - BOOLEAN
  673. 1 : pass bridged IPv6 traffic to ip6tables' chains.
  674. 0 : disable this.
  675. Default: 1
  676. bridge-nf-filter-vlan-tagged - BOOLEAN
  677. 1 : pass bridged vlan-tagged ARP/IP traffic to arptables/iptables.
  678. 0 : disable this.
  679. Default: 1
  680. UNDOCUMENTED:
  681. dev_weight FIXME
  682. discovery_slots FIXME
  683. discovery_timeout FIXME
  684. fast_poll_increase FIXME
  685. ip6_queue_maxlen FIXME
  686. lap_keepalive_time FIXME
  687. lo_cong FIXME
  688. max_baud_rate FIXME
  689. max_dgram_qlen FIXME
  690. max_noreply_time FIXME
  691. max_tx_data_size FIXME
  692. max_tx_window FIXME
  693. min_tx_turn_time FIXME
  694. mod_cong FIXME
  695. no_cong FIXME
  696. no_cong_thresh FIXME
  697. slot_timeout FIXME
  698. warn_noreply_time FIXME
  699. $Id: ip-sysctl.txt,v 1.20 2001/12/13 09:00:18 davem Exp $