linux 路由表功能解析.docx
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linux路由表功能解析
linux路由表功能解析
linux路由表功能解析分类：
网络2013-11-1618:
231268人阅读评论（0）收藏举报网络局域网路由器linux路由表功能解析本文,简单描述一下路由的作用.简单来说,路由器就是一个公交站台,公交站台上面有很多路公交.每条线路公交车又有很多站台（路由器）,你就会选择最近的一条公交出行方案,当然啦,站牌上面的路线是会经常更新,更新的事,有当地部门更新.这就是路由.一台电脑主机有路由表,路由器也有路由表,一般来说,一台主机电脑如果只有一个网卡的话,应该会有最少两条路由信息,一条是公网路由,一条是局域网路由（它是不会经过路由器的路由表的,因为它走的是链路层,所以可以解析我们在局域网内传数据,速度是很快的）.测试环境:
主机（linux）:
ip:
192.168.168.1.119netmask:
255.255.0.0另一台主机（xp）:
ip:
192.168.1.133netmask:
255.255.0.0网关:
ip:
192.168.0.3netmask:
255.255.248.0一,我们可以查看一下路由表.（route命令）[user:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0//公网路由信息//U–Up,G–Gateway,H–Host192.168.0.0*255.255.0.0U000eth0//局域网路由信息.
[user:
dvr_linux]
Flags可能出现的标志有：
U（routeisup）路由正常
H（targetisahost）主机路由
G（usegateway）使用网关的间接路由
R（reinstateroutefordynamicrouting）为动态选路恢复路由
D（dynamicallyinstalledbydaemonorredirect）该路由由选路进程或重定向动态创建
M（modifiedfromroutingdaemonorrederict）该路由已由选路进程或重定向修改
!
（rejectroute）阻塞路由
1.1测试公网路由（切换到root用户下）:
[root:
dvr_linux]route//打印路由表
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]ping8.8.8.8//8.8.8.8是google公司的dns.
PING8.8.8.8（8.8.8.8）56（84）bytesofdata.
64bytesfrom8.8.8.8:
icmp_req=2ttl=48time=10.4ms
64bytesfrom8.8.8.8:
icmp_req=3ttl=48time=10.0ms//正常
^C
---8.8.8.8pingstatistics---
3packetstransmitted,2received,33%packetloss,time2013ms
rttmin/avg/max/mdev=10.024/10.222/10.421/0.222ms
[root:
dvr_linux]routedeldefaultdeveth0//删除默认路由,也就公网路由,因为有网关.
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]ping8.8.8.8
connect:
Networkisunreachable//ping不通,没找到路由信息.数据包出不去.
[root:
dvr_linux]routeadddefaultdeveth0//增加默认路由,没加网关.
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default*0.0.0.0U000eth0
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]ping8.8.8.8
PING8.8.8.8（8.8.8.8）56（84）bytesofdata.
From192.168.1.119icmp_seq=1DestinationHostUnreachable//ping不通,找到路由信息.但是找不到去8.8.8.8胡线路,数据包出不去.
From192.168.1.119icmp_seq=2DestinationHostUnreachable
From192.168.1.119icmp_seq=3DestinationHostUnreachable
^C
---8.8.8.8pingstatistics---
5packetstransmitted,0received,+3errors,100%packetloss,time4010ms
pipe3
[root:
dvr_linux]routedeldefaultdeveth0
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]routeadddefaultgw192.168.0.3deveth0
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]ping8.8.8.8
PING8.8.8.8（8.8.8.8）56（84）bytesofdata.
64bytesfrom8.8.8.8:
icmp_req=1ttl=48time=11.0ms//重新添加带网关的路由信息后,又能ping通了.
64bytesfrom8.8.8.8:
icmp_req=3ttl=48time=10.0ms
64bytesfrom8.8.8.8:
icmp_req=4ttl=48time=10.3ms
^C
---8.8.8.8pingstatistics---
4packetstransmitted,3received,25%packetloss,time3015ms
rttmin/avg/max/mdev=10.037/10.496/11.071/0.445ms
[root:
dvr_linux]1.2测试局域网路由（切换到root用户下）:
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]ping192.168.1.133
PING192.168.1.133（192.168.1.133）56（84）bytesofdata.
64bytesfrom192.168.1.133:
icmp_req=1ttl=64time=2.13ms
64bytesfrom192.168.1.133:
icmp_req=2ttl=64time=0.450ms//正常通过.
^C
---192.168.1.133pingstatistics---
2packetstransmitted,2received,0%packetloss,time1003ms
rttmin/avg/max/mdev=0.450/1.290/2.131/0.841ms
[root:
dvr_linux]routedel-net192.168.0.0/16deveth0//删除局域网路由
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0
[root:
dvr_linux]ping192.168.1.133
PING192.168.1.133（192.168.1.133）56（84）bytesofdata.
64bytesfrom192.168.1.133:
icmp_req=1ttl=64time=5.06ms
From192.168.0.3:
icmp_seq=1RedirectHost（Newnexthop:
192.168.1.133）//数据包通过了默认路由信息发到了路由器,再查路由器的路由表找到了192.168.1.133的路由.再由网关发回来给192.168.1.133了.
64bytesfrom192.168.1.133:
icmp_req=2ttl=64time=0.477ms
64bytesfrom192.168.1.133:
icmp_req=3ttl=64time=0.302ms
64bytesfrom192.168.1.133:
icmp_req=4ttl=64time=0.285ms
64bytesfrom192.168.1.133:
icmp_req=5ttl=64time=0.478ms
64bytesfrom192.168.1.133:
icmp_req=6ttl=64time=0.408ms
^C
---192.168.1.133pingstatistics---
6packetstransmitted,6received,0%packetloss,time5002ms
rttmin/avg/max/mdev=0.285/1.169/5.066/1.744ms
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0
[root:
dvr_linux]routedeldefaulteth0//把默认路由都删掉的话,这就完全找不到路由信息了,也就是没网络了.
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
[root:
dvr_linux]ping192.168.1.133
connect:
Networkisunreachable
[root:
dvr_linux]
在这个时候,192.168.1.133的xp主机去ping192.168.1.119的话.也就ping不通的.C:
\DocumentsandSettings\Administrator>ping192.168.1.119-tPinging192.168.1.119with32bytesofdata:
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.[root:
dvr_linux]servicenetworkingrestart//重启一下网络.
[warn]Running/etc/init.d/networkingrestartisdeprecatedbecauseitmaynotre-enablesomeinterfaces...（warning）.
[....]Reconfiguringnetworkinterfaces...RTNETLINKanswers:
Nosuchprocess
done.
[root:
dvr_linux]
[root:
dvr_linux]route
KernelIProutingtable
DestinationGatewayGenmaskFlagsMetricRefUseIface
default192.168.0.30.0.0.0UG000eth0
192.168.0.0*255.255.0.0U000eth0
[root:
dvr_linux]在这个时候,192.168.1.133的xp主机去ping192.168.1.119的话.网络恢复了.C:
\DocumentsandSettings\Administrator>ping192.168.1.119-tPinging192.168.1.119with32bytesofdata:
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Requesttimedout.
Replyfrom192.168.1.119:
bytes=32time=2msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time=6msTTL=63
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
Replyfrom192.168.1.119:
bytes=32time<1msTTL=64
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