關於Linux路由表的route命令(轉)

標籤：

　 查看 Linux 核心路由表　　使用下面的 route 命令可以查看 Linux 核心路由表。　　# route　　Destination  Gateway      Genmask          Flags Metric Ref Use Iface　　192.168.0.0   *                 255.255.255.0  U        0         0     0    eth0　　169.254.0.0   *                 255.255.0.0      U        0         0     0    eth0　　default        192.168.0.1   0.0.0.0              UG     0         0     0    eth0　　route 命令的輸出項說明　　輸出項             說明　　Destination      目標網段或者主機　　Gateway          網關地址，”*” 表示目標是本主機所屬的網路，不需要路由　　Genmask         網路遮罩　　Flags               標記　　一些可能的標記如下：　　U — 路由是活動的　　H — 目標是一個主機　　N — 目標時某個網段　　G — 路由指向網關　　R — 恢複動態路由產生的表項　　D — 由路由的背景程式動態地安裝　　M — 由路由的背景程式修改　　! — 拒絕路由　　Metric 路由距離，到達指定網路所需的中轉數（linux 核心中沒有使用）。　　Ref 路由項引用次數（linux 核心中沒有使用）。　　Use 此路由項被路由軟體尋找的次數 。　　Iface 該路由表項對應的輸出介面 。　　*******************************************************************************************************************************　　 3 種路由類型　　主機路由　　主機路由是路由選擇表中指向單個IP地址或主機名稱的路由記錄。主機路由的Flags欄位為H。例如，在下面的樣本　　中，本地主機通過IP地址192.168.1.1的路由器到達IP地址為10.0.0.10的主機。　　Destination Gateway     Genmask              Flags   Metric Ref Use Iface　　-----------      -------           -------                    -----      ------    ---   ---    -----　　10.0.0.10   192.168.1.1 255.255.255.255  UH       0         0     0     eth0　　網路路由　　網路路由是代表主機可以到達的網路。網路路由的Flags欄位為N。例如，在下面的樣本中，本地主機將發送到網　　絡192.19.12的資料包轉寄到IP地址為192.168.1.1的路由器。　　Destination Gateway       Genmask          Flags Metric Ref Use Iface　　-----------      -------             -------                -----    -----     ---   ---    -----　　192.19.12   192.168.1.1  255.255.255.0  UN     0        0     0      eth0　　預設路由　　當主機不能在路由表中尋找到目標主機的IP地址或網路路由時，資料包就被發送到預設路由（預設閘道）上。默　　認路由的Flags欄位為G。例如，在下面的樣本中，預設路由是IP地址為192.168.1.1的路由器。　　Destination Gateway      Genmask Flags  Metric Ref Use Iface　　-----------      -------            -------        -----     ------   ---   ---    -----　　default        192.168.1.1  0.0.0.0     UG     0         0    0      eth0　　*******************************************************************************************************************************　 　配置靜態路由　　route 命令　　設定和查看路由表都可以用 route 命令，設定核心路由表的命令格式是：　　# route [add|del] [-net|-host] target [netmask Nm] [gw Gw] [[dev] If]　　其中：　　add : 添加一條路由規則　　del : 刪除一條路由規則　　-net : 目的地址是一個網路　　-host : 目的地址是一個主機　　target : 目的網路或主機　　netmask : 目的地址的網路遮罩　　gw : 路由資料包通過的網關　　dev : 為路由指定的網路介面　　route 命令使用舉例　　添加到主機的路由　　# route add -host 192.168.1.2 dev eth0:0　　# route add -host 10.20.30.148 gw 10.20.30.40　　添加到網路的路由　　# route add -net 10.20.30.40 netmask 255.255.255.248 eth0　　# route add -net 10.20.30.48 netmask 255.255.255.248 gw 10.20.30.41　　# route add -net 192.168.1.0/24 eth1　　添加預設路由　　# route add default gw 192.168.1.1　　刪除路由　　# route del -host 192.168.1.2 dev eth0:0　　# route del -host 10.20.30.148 gw 10.20.30.40　　# route del -net 10.20.30.40 netmask 255.255.255.248 eth0　　# route del -net 10.20.30.48 netmask 255.255.255.248 gw 10.20.30.41　　# route del -net 192.168.1.0/24 eth1　　# route del default gw 192.168.1.1　　*******************************************************************************************************************************　 　設定包轉寄　　在 CentOS 中預設的核心配置已經包含了路由功能，但預設並沒有在系統啟動時啟用此功能。開啟 Linux的路由　　功能可以通過調整核心的網路參數來實現。要配置和調整核心參數可以使用 sysctl 命令。例如：要開啟 Linux核心的　　資料包轉寄功能可以使用如下的命令。　　# sysctl -w net.ipv4.ip_forward=1　　這樣設定之後，當前系統就能實現包轉寄，但下次啟動電腦時將失效。為了使在下次啟動電腦時仍然有效，　　需要將下面的行寫入設定檔/etc/sysctl.conf。　　# vi /etc/sysctl.conf　　net.ipv4.ip_forward = 1　　使用者還可以使用如下的命令查看當前系統是否支援包轉寄。　　# sysctl net.ipv4.ip_forward http://pda158.iteye.com/blog/2173154 

ROUTE(8) Linux Programmer’s Manual ROUTE(8)

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]

NOTE
This program is obsolete. For replacement check ip route.

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 van-
ished.

-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 before-
hand. 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 sets MTU (Maximum Transmission Unit) of the route to M bytes. Note that the current implementation of the route command does not allow the option to set the Maximum
Segment Size (MSS).

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 actu-
ally 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 config-
uration 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
ip(8)

HISTORY
Route for Linux was originally written by Fred N. van Kempen, <[email protected]> and then modified by Johannes Stille and Linus Torvalds for pl15. Alan Cox added
the mss and window options for Linux 1.1.22. irtt support and merged with netstat from Bernd Eckenfels.

AUTHOR
Currently maintained by Phil Blundell <[email protected]>.

 

 

關於Linux路由表的route命令(轉)