diff options
Diffstat (limited to 'Documentation/networking/ip-sysctl.txt')
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 65 |
1 files changed, 56 insertions, 9 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index f350c69..d99940d 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -11,7 +11,9 @@ ip_forward - BOOLEAN for routers) ip_default_ttl - INTEGER - default 64 + Default value of TTL field (Time To Live) for outgoing (but not + forwarded) IP packets. Should be between 1 and 255 inclusive. + Default: 64 (as recommended by RFC1700) ip_no_pmtu_disc - BOOLEAN Disable Path MTU Discovery. @@ -20,6 +22,15 @@ ip_no_pmtu_disc - BOOLEAN min_pmtu - INTEGER default 562 - minimum discovered Path MTU +route/max_size - INTEGER + Maximum number of routes allowed in the kernel. Increase + this when using large numbers of interfaces and/or routes. + +neigh/default/gc_thresh3 - INTEGER + Maximum number of neighbor entries allowed. Increase this + when using large numbers of interfaces and when communicating + with large numbers of directly-connected peers. + mtu_expires - INTEGER Time, in seconds, that cached PMTU information is kept. @@ -135,6 +146,7 @@ tcp_adv_win_scale - INTEGER Count buffering overhead as bytes/2^tcp_adv_win_scale (if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale), if it is <= 0. + Possible values are [-31, 31], inclusive. Default: 2 tcp_allowed_congestion_control - STRING @@ -698,10 +710,28 @@ igmp_max_memberships - INTEGER Change the maximum number of multicast groups we can subscribe to. Default: 20 -conf/interface/* changes special settings per interface (where "interface" is - the name of your network interface) -conf/all/* is special, changes the settings for all interfaces + Theoretical maximum value is bounded by having to send a membership + report in a single datagram (i.e. the report can't span multiple + datagrams, or risk confusing the switch and leaving groups you don't + intend to). + + The number of supported groups 'M' is bounded by the number of group + report entries you can fit into a single datagram of 65535 bytes. + + M = 65536-sizeof (ip header)/(sizeof(Group record)) + + Group records are variable length, with a minimum of 12 bytes. + So net.ipv4.igmp_max_memberships should not be set higher than: + + (65536-24) / 12 = 5459 + + The value 5459 assumes no IP header options, so in practice + this number may be lower. + + conf/interface/* changes special settings per interface (where + "interface" is the name of your network interface) + conf/all/* is special, changes the settings for all interfaces log_martians - BOOLEAN Log packets with impossible addresses to kernel log. @@ -1014,6 +1044,12 @@ conf/interface/*: accept_ra - BOOLEAN Accept Router Advertisements; autoconfigure using them. + Possible values are: + 0 Do not accept Router Advertisements. + 1 Accept Router Advertisements if forwarding is disabled. + 2 Overrule forwarding behaviour. Accept Router Advertisements + even if forwarding is enabled. + Functional default: enabled if local forwarding is disabled. disabled if local forwarding is enabled. @@ -1075,7 +1111,12 @@ forwarding - BOOLEAN Note: It is recommended to have the same setting on all interfaces; mixed router/host scenarios are rather uncommon. - FALSE: + Possible values are: + 0 Forwarding disabled + 1 Forwarding enabled + 2 Forwarding enabled (Hybrid Mode) + + FALSE (0): By default, Host behaviour is assumed. This means: @@ -1085,18 +1126,24 @@ forwarding - BOOLEAN Advertisements (and do autoconfiguration). 4. If accept_redirects is TRUE (default), accept Redirects. - TRUE: + TRUE (1): If local forwarding is enabled, Router behaviour is assumed. This means exactly the reverse from the above: 1. IsRouter flag is set in Neighbour Advertisements. 2. Router Solicitations are not sent. - 3. Router Advertisements are ignored. + 3. Router Advertisements are ignored unless accept_ra is 2. 4. Redirects are ignored. - Default: FALSE if global forwarding is disabled (default), - otherwise TRUE. + TRUE (2): + + Hybrid mode. Same behaviour as TRUE, except for: + + 2. Router Solicitations are being sent when necessary. + + Default: 0 (disabled) if global forwarding is disabled (default), + otherwise 1 (enabled). hop_limit - INTEGER Default Hop Limit to set. |