NAME

route - 顯示 / 操作IP選路表

總覽 SYNOPSIS

route [-CFvnee]

route [-v] [-A         family] add [-net|-host] target [netmask Nm] [gw Gw] [metric N] [mss M] [window W] [irtt I][reject] [mod] [dyn] [reinstate] [[dev] If]
 

route [-v] [-A         family] del [-net|-host] target [gw Gw][netmask Nm] [metric N] [[dev] If]
 

route [-V] [--version] [-h] [--help]

描述 DESCRIPTION

route程序對內核的IP選路表進行操作。它主要用于通過已用ifconfig(8)程序配置好的接口來指定的主機或網絡設置靜態路由。

選項 OPTIONS

-v

選用細節操作模式

-A family

用指定的地址族(如`inet'，`inet6')。

-n

以數字形式代替解釋主機名形式來顯示地址。此項對試圖檢測對域名服務器進行路由發生故障的原因非常有用。

-e

用netstat(8)的格式來顯示選路表。-ee將產生包括選路表所有參數在內的大量信息。

-net

路由目標為網絡。

-host

路由目標為主機。

-F

顯示內核的FIB選路表。其格式可以用-e 和 -ee選項改變。

-C

顯示內核的路由緩存。

del

刪除一條路由。

add

添加一條路由。

target

指定目標網絡或主機。可以用點分十進制形式的IP地址或主機/網絡名。

netmask Nm

為添加的路由指定網絡掩碼。

gw Gw

為發往目標網絡/主機的任何分組指定網關。注意：指定的網關首先必須是可達的。也就是說必須為該網關預先指定一條靜態路由。如果你為本地接口之一指定這個網關地址的話，那么此網關地址將用于決定此接口上的分組將如何進行路由。這是BSD風格所兼容的。

metric M

把選路表中的路由值字段(由選路進程使用)設為M。

mss M

把基于此路由之上的連接的TCP***報文段長度設為M字節。這通常只用于優化選路設置。默認值為536。

window W

把基于此路由之上的連接的TCP窗口長度設為W字節。這通常只用于AX.25網絡和不能處理背對背形式的幀的設備。

irtt I

把基于此路由之上的TCP連接的初始往返時間設為I毫秒(1-12000)。這通常也只用于AX.25網絡。如果省略此選項，則使用RFC1122的缺省值300ms。

reject

設置一條阻塞路由以使一條路由查找失敗。這用于在使用缺省路由前先屏蔽掉一些網絡。但這并不起到防火墻的作用。

mod, dyn, reinstate

設置一條動態的或更改過的路由。這些標志通常只由選路進程來設置。這只用于診斷目的，

dev If

強制使路由與指定的設備關聯，因為否則內核會自己來試圖檢測相應的設備(通常檢查已存在的路由和加入路由的設備的規格)。在多數正常的網絡上無需使用。

如果dev If是命令行上***一個指定的選項，那么可以省略關鍵字dev，因為它是缺省值。否則路由修改對象(metric - netmask- gw - dev)無關緊要。

范例 EXAMPLES

route add -net 127.0.0.0

加入正常的環回接口項，它使用掩碼255.0.0.0(由目標地址決定了它是A類網絡)并與設備"lo"相關聯(假定該設備先前已由ifconfig(8)正確設置)。

route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0

向"eth0"添加一條指向網絡192.56.76.x的路由。其中的C類子網掩碼并不必須，因為192.*是個C類的IP地址。在此關鍵字"dev"可省略。

route add default gw mango-gw

加入一條缺省路由(如果無法匹配其它路由則用它)。使用此路由的所有分組將通過網關"mango-gw"進行傳輸。實際使用此路由的設備取決于如何到達"mango-gw" - 先前必須設好到"mango-gw"的靜態路由。

route add ipx4 sl0

向SLIP接口添加一條指向"ipx4"的路由(假定"ipx4"是使用SLIP的主機)。

route add -net 192.57.66.0 netmask 255.255.255.0 gw ipx4

此命令為先前SLIP接口的網關ipx4添加到網絡"192.57.66.x"的路由。

route add 224.0.0.0 netmask 240.0.0.0 dev eth0

此命令為"eth0"設定所有D類地址(用于組播)的路由。這是用于組播內核的正確配置行。

route add 10.0.0.0 netmask 255.0.0.0 reject

此命令為私有網絡"10.x.x.x."設置一條阻塞路由。

輸出信息 OUTPUT

內核選路表的輸出信息由以下欄目組成：

Destination

目標網絡或目標主機。

Gateway

網關地址或'*'(如未設)。

Genmask

目標網絡的子網掩碼；'255.255.255.255'為主機，'0.0.0.0'為缺省路由。

Flags

可能出現的標志有：
U (route is up) 路由正常
H (target is a host) 主機路由
G (use gateway) 使用網關的間接路由
R (reinstate route for dynamic routing) 為動態選路恢復路由
D (dynamically installed by daemon or redirect) 該路由由選路進程或重定向動態創建
M (modified from routing daemon or rederict) 該路由已由選路進程或重定向修改
! (reject route) 阻塞路由

Metric

通向目標的距離(通常以跳來計算)。新內核不使用此概念，而選路進程可能會用。

Ref

使用此路由的活動進程個數(Linux內核并不使用)。

Use

查找此路由的次數。根據-F 和 -C的使用，此數值是路由緩存的損失數或采樣數。

Iface

使用此路由發送分組的接口。

MSS

基于此路由的TCP連接的缺省***報文段長度。

Window

基于此路由的TCP連接的缺省窗口長度。

irtt

初始往返時間。內核用它來猜測***TCP協議參數而無須等待(可能很慢的)應答。

HH (cached only)

為緩存過的路由而訪問硬件報頭緩存的ARP記錄和緩存路由的數量。如果緩存過路由的接口(如lo)無須硬件地址則值為-1。

Arp (cached only)

無論緩存路由所用的硬件地址情況如何都進行更新。

文件 FILES

/proc/net/ipv6_route
/proc/net/route
/proc/net/rt_cache
 

參見SEE ALSO

ifconfig(8), netstat(8), arp(8), rarp(8)

#p#

NAME

route - show / manipulate the IP routing table  

SYNOPSIS

route [-CFvnee]

route

[-v] [-A family] add [-net|-host] target [netmask Nm] [gw Gw] [metric N] [mss M] [window W] [irtt I] [reject] [mod] [dyn] [reinstate] [[dev] If]

route

[-v] [-A family] del [-net|-host] target [gw Gw] [netmask Nm] [metric N] [[dev] If]

route

[-V] [--version] [-h] [--help]

DESCRIPTION

Route manipulates the kernel's IP routing tables. Its primary use is to set up static routes to specific hosts or networks via an interface after it has been configured with the ifconfig(8) program.

When the add or del options are used, route modifies the routing tables. Without these options, route displays the current contents of the routing tables.

OPTIONS

-A family

use the specified address family (eg `inet'; use `route --help' for a full list).

-F

operate on the kernel's FIB (Forwarding Information Base) routing table. This is the default.

-C

operate on the kernel's routing cache.

-v

select verbose operation.

-n

show numerical addresses instead of trying to determine symbolic host names. This is useful if you are trying to determine why the route to your nameserver has vanished.

-e

use netstat(8)-format for displaying the routing table. -ee will generate a very long line with all parameters from the routing table.

del

delete a route.

add

add a new route.

target

the destination network or host. You can provide IP addresses in dotted decimal or host/network names.

-net

the target is a network.

-host

the target is a host.

netmask NM

when adding a network route, the netmask to be used.

gw GW

route packets via a gateway. NOTE: The specified gateway must be reachable first. This usually means that you have to set up a static route to the gateway beforehand. If you specify the address of one of your local interfaces, it will be used to decide about the interface to which the packets should be routed to. This is a BSDism compatibility hack.

metric M

set the metric field in the routing table (used by routing daemons) to M.

mss M

set the TCP Maximum Segment Size (MSS) for connections over this route to M bytes. The default is the device MTU minus headers, or a lower MTU when path mtu discovery occured. This setting can be used to force smaller TCP packets on the other end when path mtu discovery does not work (usually because of misconfigured firewalls that block ICMP Fragmentation Needed)

window W

set the TCP window size for connections over this route to W bytes. This is typically only used on AX.25 networks and with drivers unable to handle back to back frames.

irtt I

set the initial round trip time (irtt) for TCP connections over this route to I milliseconds (1-12000). This is typically only used on AX.25 networks. If omitted the RFC 1122 default of 300ms is used.

reject

install a blocking route, which will force a route lookup to fail. This is for example used to mask out networks before using the default route. This is NOT for firewalling.

mod, dyn, reinstate

install a dynamic or modified route. These flags are for diagnostic purposes, and are generally only set by routing daemons.

dev If

force the route to be associated with the specified device, as the kernel will otherwise try to determine the device on its own (by checking already existing routes and device specifications, and where the route is added to). In most normal networks you won't need this.

If dev If is the last option on the command line, the word dev may be omitted, as it's the default. Otherwise the order of the route modifiers (metric - netmask - gw - dev) doesn't matter.

EXAMPLES

route add -net 127.0.0.0

adds the normal loopback entry, using netmask 255.0.0.0 (class A net, determined from the destination address) and associated with the "lo" device (assuming this device was prviously set up correctly with ifconfig(8)).

route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0

adds a route to the network 192.56.76.x via "eth0". The Class C netmask modifier is not really necessary here because 192.* is a Class C IP address. The word "dev" can be omitted here.

route add default gw mango-gw

adds a default route (which will be used if no other route matches). All packets using this route will be gatewayed through "mango-gw". The device which will actually be used for that route depends on how we can reach "mango-gw" - the static route to "mango-gw" will have to be set up before.

route add ipx4 sl0

Adds the route to the "ipx4" host via the SLIP interface (assuming that "ipx4" is the SLIP host).

route add -net 192.57.66.0 netmask 255.255.255.0 gw ipx4

This command adds the net "192.57.66.x" to be gatewayed through the former route to the SLIP interface.

route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0

This is an obscure one documented so people know how to do it. This sets all of the class D (multicast) IP routes to go via "eth0". This is the correct normal configuration line with a multicasting kernel.

route add -net 10.0.0.0 netmask 255.0.0.0 reject

This installs a rejecting route for the private network "10.x.x.x."

OUTPUT

The output of the kernel routing table is organized in the following columns

Destination

The destination network or destination host.

Gateway

The gateway address or '*' if none set.

Genmask

The netmask for the destination net; '255.255.255.255' for a host destination and '0.0.0.0' for the default route.

Flags

Possible flags include
U (route is up)
H (target is a host)
G (use gateway)
R (reinstate route for dynamic routing)
D (dynamically installed by daemon or redirect)
M (modified from routing daemon or redirect)
A (installed by addrconf)
C (cache entry)
! (reject route)

Metric

The 'distance' to the target (usually counted in hops). It is not used by recent kernels, but may be needed by routing daemons.

Ref

Number of references to this route. (Not used in the Linux kernel.)

Use

Count of lookups for the route. Depending on the use of -F and -C this will be either route cache misses (-F) or hits (-C).

Iface

Interface to which packets for this route will be sent.

MSS

Default maximum segement size for TCP connections over this route.

Window

Default window size for TCP connections over this route.

irtt

Initial RTT (Round Trip Time). The kernel uses this to guess about the best TCP protocol parameters without waiting on (possibly slow) answers.

HH (cached only)

The number of ARP entries and cached routes that refer to the hardware header cache for the cached route. This will be -1 if a hardware address is not needed for the interface of the cached route (e.g. lo).

Arp (cached only)

Whether or not the hardware address for the cached route is up to date.

FILES

/proc/net/ipv6_route
/proc/net/route
/proc/net/rt_cache

SEE ALSO

ifconfig(8), netstat(8), arp(8), rarp(8)