本文鏈接：http://codingstandards.iteye.com/blog/1125312 （轉載請註明出處）
用途說明
route命令用於顯示和操作IP路由表（show / manipulate the IP routing table）。要實現兩個不同的子網之間的通信，需要一臺連接兩個網絡的路由器，或者同時位於兩個網絡的網關來實現。在Linux系統中，設置路由通常是爲了解決以下問題：該Linux系統在一個局域網中，局域網中有一個網關，能夠讓機器訪問Internet，那麼就需要將這臺機器的IP地址設置爲Linux機器的默認路由。要注意的是，直接在命令行下執行route命令來添加路由，不會永久保存，當網卡重啓或者機器重啓之後，該路由就失效了；可以在/etc/rc.local中添加route命令來保證該路由設置永久有效。本文中的例子中會驗證這一點。
常用參數
格式：route
格式：/sbin/route
用於打印路由表（display the current routing table）。
在非root用戶使用時需要使用完整路徑執行route命令。
格式：route -n
格式：/sbin/route -n
用於打印路由表，加上-n參數就是在輸出的信息中不打印主機名而直接打印ip地址。像netstat命令也有此參數。
格式：route add default gw {IP-ADDRESS} {INTERFACE-NAME}
用於設置默認路由（adds a default route, which will be used if no other route matches），其中，
參數{IP-ADDRESS): 用於指定路由器（網關）的IP地址（Specify router IP address）；
參數{INTERFACE-NAME}: 用於指定接口名稱，如eth0（Specify interface name such as eth0）。使用/sbin/ifconfig -a可以顯示所有接口信息。
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.
格式：route add -net {NETWORK-ADDRESS} netmask {NETMASK} dev {INTERFACE-NAME}
添加到指定網絡的路由規則，其中
參數{NETWORK-ADDRESS}: 用於指定網絡地址
參數{NETMASK}: 用於指定子網掩碼
參數{INTERFACE-NAME}: 用於指定接口名稱，如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 -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.
格式：route add -net {NETWORK-ADDRESS} netmask {NETMASK} reject
設置到指定網絡爲不可達，避免在連接到這個網絡的地址時程序過長時間的等待，直接就知道該網絡不可達。
This installs a rejecting route for the private network "10.x.x.x."
格式：route del -net {NETWORK-ADDRESS} netmask {NETMASK} dev {INTERFACE-NAME}
格式：route del -net {NETWORK-ADDRESS} netmask {NETMASK} reject
用於刪除路由設置。參數指定的方式與route add相似。
route命令輸出的路由表字段含義如下：
Destination 目標
The destination network or destination host. 目標網絡或目標主機。
Gateway 網關
The gateway address or '*' if none set. 網關地址，如果沒有就顯示星號。
Genmask 網絡掩碼
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 標誌，常用的是U和G。
U (route is up) 路由啓用
H (target is a host) 目標是主機
G (use gateway) 使用網關
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 距離、跳數。暫無用。
The 'distance' to the target (usually counted in hops). It is
not used by recent kernels, but may be needed by routing dae-
mons.
Ref 不用管，恆爲0。
Number of references to this route. (Not used in the Linux ker-
nel.)
Use 該路由被使用的次數，可以粗略估計通向指定網絡地址的網絡流量。
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 接口，即eth0,eth0等網絡接口名
Interface to which packets for this route will be sent.
使用示例
示例一 打印當前路由表（root用戶）
[root@jfht ~]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
211.103.28.0 * 255.255.255.224 U 0 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
default 211.103.28.1 0.0.0.0 UG 0 0 0 eth0
[root@jfht ~]# /sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
211.103.28.0 * 255.255.255.224 U 0 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
default 211.103.28.1 0.0.0.0 UG 0 0 0 eth0
[root@jfht ~]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
211.103.28.0 0.0.0.0 255.255.255.224 U 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
0.0.0.0 211.103.28.1 0.0.0.0 UG 0 0 0 eth0
[root@jfht ~]# /sbin/route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
211.103.28.0 0.0.0.0 255.255.255.224 U 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
0.0.0.0 211.103.28.1 0.0.0.0 UG 0 0 0 eth0
[root@jfht ~]#
示例二 打印當前路由表（非root用戶）
[web@hnweb1 ~]$ route
-bash: route: command not found
[web@hnweb1 ~]$ /sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.66.10.0 * 255.255.255.128 U 0 0 0 eth0
192.130.12.0 10.66.10.1 255.255.255.0 UG 0 0 0 eth0
10.0.0.0 * 255.255.255.0 U 0 0 0 eth1
10.66.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
134.161.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
10.20.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
172.224.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
default 10.66.10.22 0.0.0.0 UG 0 0 0 eth0
[web@hnweb1 ~]$ route -n
-bash: route: command not found
[web@hnweb1 ~]$ /sbin/route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.66.10.0 0.0.0.0 255.255.255.128 U 0 0 0 eth0
192.130.12.0 10.66.10.1 255.255.255.0 UG 0 0 0 eth0
10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
10.66.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
134.161.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
10.20.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
172.224.0.0 10.66.10.1 255.255.0.0 UG 0 0 0 eth0
0.0.0.0 10.66.10.22 0.0.0.0 UG 0 0 0 eth0
[web@hnweb1 ~]$
示例三 設置到某網絡的路由的例子
下面的例子 來自一個實際的服務器配置。 route命令寫在了/etc/rc.local中，這樣就設置了一條永久路由。
[root@jf07 root]# grep route /etc/rc.local
route add -net 10.0.0.0/8 gw 10.33.149.1 dev eth1
[root@jf07 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.32.181.182 10.33.149.1 255.255.255.255 UGH 0 0 0 eth1
10.33.136.135 10.33.149.1 255.255.255.255 UGH 0 0 0 eth1
10.32.208.13 10.33.149.1 255.255.255.255 UGH 0 0 0 eth1
10.33.149.0 * 255.255.255.128 U 0 0 0 eth1
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
10.0.0.0 10.33.149.1 255.0.0.0 UG 0 0 0 eth1
default 192.168.1.254 0.0.0.0 UG 0 0 0 eth0
[root@jf07 root]#
示例四 添加拒絕路由的測試
[root@jfht ~]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
211.103.28.0 * 255.255.255.224 U 0 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
default 211.103.28.1 0.0.0.0 UG 0 0 0 eth0
[root@jfht ~]# ping 10.33.11.12
PING 10.33.11.12 (10.33.11.12) 56(84) bytes of data.
Ctrl+C
--- 10.33.11.12 ping statistics ---
21 packets transmitted, 0 received, 100% packet loss, time 19999ms
[root@jfht ~]# route add -net 10.0.0.0 netmask 255.0.0.0 reject
[root@jfht ~]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
211.103.28.0 * 255.255.255.224 U 0 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
10.0.0.0 - 255.0.0.0 ! 0 - 0 -
default 211.103.28.1 0.0.0.0 UG 0 0 0 eth0
[root@jfht ~]# ping 10.33.11.12
connect: Network is unreachable
[root@jfht ~]#
示例五 設置路由之後重啓機器的測試
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]# route add -net 10.0.0.0 netmask 255.0.0.0 reject
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
10.0.0.0 - 255.0.0.0 ! 0 - 0 -
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]# reboot
Broadcast message from root (pts/0) (Thu Jul 7 05:31:26 2011):
The system is going down for reboot NOW!
[root@node34 root]#
Last login: Thu Jul 7 05:30:50 2011 from 192.168.227.1
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]#
上面的測試表明route設置的路由在機器重啓之後就消失了。
示例六 將route命令添加到/etc/rc.local來設置永久路由的測試
先用vi在/etc/rc.local後面添加route命令。
[root@node34 root]# tail /etc/rc.local
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
# 2011.07.15 add permanent route test
route add -net 10.0.0.0 netmask 255.0.0.0 reject
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]# reboot
Broadcast message from root (pts/0) (Fri Jul 15 14:43:44 2011):
The system is going down for reboot NOW!
[root@node34 root]#
Last login: Fri Jul 15 14:40:22 2011 from 192.168.227.1
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
10.0.0.0 - 255.0.0.0 ! 0 - 0 -
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]#
示例七 刪除路由的測試
刪除路由的時候只需將route add改成route del，其他參數類似。如果報“無效的參數”或“沒有那個進程”，可能是因爲提供的參數不夠。
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
10.0.0.0 - 255.0.0.0 ! 0 - 0 -
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]#
[root@node34 root]# route del -net 10.0.0.0
SIOCDELRT: 無效的參數
[root@node34 root]# route del -net 10.0.0.0 netmask 255.0.0.0
SIOCDELRT: 沒有那個進程
[root@node34 root]#
[root@node34 root]# route del -net 10.0.0.0 netmask 255.0.0.0 reject
[root@node34 root]#
[root@node34 root]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.227.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
default 192.168.227.2 0.0.0.0 UG 0 0 0 eth0
[root@node34 root]#
問題思考
相關資料
【1】nixCraft Linux setup default gateway with route command
http://www.cyberciti.biz/faq/linux-setup-default-gateway-with-route-command/
【2】360doc Linux route命令
http://www.360doc.com/content/11/0418/14/2054285_110501874.shtml
【3】Linux公社 Linux下route add route del 用法
http://www.linuxidc.com/Linux/2010-11/30032.htm
【4】鳥哥的 Linux 私房菜 第五章、 Linux 常用網路指令
http://linux.vbird.org/linux_server/0140networkcommand.php#route
轉載自：http://codingstandards.iteye.com/blog/1125312