路由器介绍

路由器的工作原理

1、路由器的工作原理：路由器接收数据包，提取目标IP地址及子网掩码计算目标网络地址；根据目标网络地址查找路由表，若找到目标网络地址，按照相应的出口发送到下一个路由器；若未找到，观察是否有默认路由，按照默认路由的出口发送给下一个路由器，若未找到给源IP，发送出错ICMP数据包表明无法传递该数据包；若为直连路由就按照第二层MAC地址发送给目标站点。

2、路由器的工作特点：连接多个网络或网段的网络设备，将不同网络或网段之间的数据信息进行翻译，可相互读懂对方的数据。

静态路由和默认路由

静态路由

1.由管理员手工配置的，是单向的
2.缺乏灵活性

默认路由

当路由器在路由表中找不到目标网络的路由条月时，路由器把请求转发到默认路由接口

路由器转发数据包的封装过程

1.主机1项主机2发送数据，主机1在网络层将来自上层的报文封装成IP数据包，其首部包含源地址和目的地址。主机1会用本地配置的24位掩码和目的地址进行”与“运算，得出目的地址和本机地址不在同一频段，因此发往主机2的数据包需要经过网关路由器A转发。
2.主机1通过ARP请求获得默认网关路由器A的E0接口MAC地址。在数据链路层主机1将IP数据包封装成以太网数据帧，那以太网帧首部的源MAC地址就是主机1的MAC地址，目的地址的MAC地址就变成了网关E0接口的MAC地址。
3.路由器A从E0接口接收到数据帧，把数据链路层的封装去掉。路由器A认为IP数据包要通过自己进行路由转发，所以路由器A会查找自己的路由表，寻找于目标IP地址相匹配的路由表项，然后根据路由表的下一跳地址将数据包转发到E1接口。
4.E1接口路由器A重新封装以太网帧，此时源MAC地址就变成了路由器A的E1接口的MAC地址，目的地址为与之相连的路由器B的E1接口的MAC地址。
5. 路由器B从E1接口收到数据帧，同样会把数据链路层的封装去掉，对目的IP地址进行检查，并与路由表进行匹配，然后根据路由表的下一跳信息将数据包转发到E0接口。路由器B发现目的网段与自己的E0接口直接相连，通过ARP广播路由器B获得了主机2以太口的MAC地址。
6. 6.路由器B再把IP数据包封装成以太网帧，这时源MAC地址就是路由器B接口E0的MAV地址，目的MAC地址就是主机2的MAC地址，然后发过去。

静态路由和默认路由的配置

R8

1

<Huawei>sys	
<Huawei>system-view 
Enter system view, return user view with Ctrl+Z.
[Huawei]sys	
[Huawei]sysname R8
[R8]inter	
[R8]interface g0/0/1
[R8-GigabitEthernet0/0/1]ip add	
[R8-GigabitEthernet0/0/1]ip address 192.168.20.2 24
Apr  6 2021 16:47:43-08:00 R8 %%01IFNET/4/LINK_STATE(l)[2]:The line protocol IP 
on the interface GigabitEthernet0/0/1 has entered the UP state. 
[R8-GigabitEthernet0/0/1]q
[R8]interface g0/0/0
[R8-GigabitEthernet0/0/0]ip address 192.168.40.1 24
Apr  6 2021 16:48:02-08:00 R8 %%01IFNET/4/LINK_STATE(l)[3]:The line protocol IP 
on the interface GigabitEthernet0/0/0 has entered the UP state. 
[R8-GigabitEthernet0/0/0]q
[R8]ip rout	
[R8]ip route-s	
[R8]ip route-static 192.168.10.0 24 192.168.40.2
[R8]ip route-static 192.168.30.0 24 192.168.40.2

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R10

<Huawei>sys	
<Huawei>system-view 
Enter system view, return user view with Ctrl+Z.
[Huawei]sys	
[Huawei]sysname R10
[R10]inter	
[R10]interface 
               ^
Error:Incomplete command found at '^' position.
[R10]interface g0/0/0
[R10-GigabitEthernet0/0/0]ip add	
[R10-GigabitEthernet0/0/0]ip address 192.168.40.2 24
Apr  6 2021 16:48:51-08:00 R10 %%01IFNET/4/LINK_STATE(l)[0]:The line protocol IP
 on the interface GigabitEthernet0/0/0 has entered the UP state. 
[R10-GigabitEthernet0/0/0]q
[R10]inter	
[R10]interface g0/0/1
[R10-GigabitEthernet0/0/1]ip add	
[R10-GigabitEthernet0/0/1]ip address 192.168.10.2 24
Apr  6 2021 16:49:29-08:00 R10 %%01IFNET/4/LINK_STATE(l)[1]:The line protocol IP
 on the interface GigabitEthernet0/0/1 has entered the UP state. 
[R10-GigabitEthernet0/0/1]q
[R10]ip rout	
[R10]ip route-s	
[R10]ip route-static 192.168.20.0 24 192.168.40.1
[R10]inter	
[R10]interface g0/0/2
[R10-GigabitEthernet0/0/2]ip add	
[R10-GigabitEthernet0/0/2]ip address 192.168.50.2 24
Apr  6 2021 16:52:28-08:00 R10 %%01IFNET/4/LINK_STATE(l)[2]:The line protocol IP
 on the interface GigabitEthernet0/0/2 has entered the UP state. 
[R10-GigabitEthernet0/0/2]

  Please check whether system data has been changed, and save data in time

  Configuration console time out, please press any key to log on

<R10>
<R10>sys	
<R10>system-view 
Enter system view, return user view with Ctrl+Z.
[R10]ip rou	
[R10]ip route-s	
[R10]ip route-static 192.168.30.0 24 192.168.50.1

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R9

1

<Huawei>sys	
<Huawei>system-view 
Enter system view, return user view with Ctrl+Z.
[Huawei]sys R9
[R9]inter	
[R9]interface g0/0/0
[R9-GigabitEthernet0/0/0]ip add	
[R9-GigabitEthernet0/0/0]ip address 192.168.50.1 24
Apr  6 2021 16:54:28-08:00 R9 %%01IFNET/4/LINK_STATE(l)[0]:The line protocol IP 
on the interface GigabitEthernet0/0/0 has entered the UP state. 
[R9-GigabitEthernet0/0/0]q
[R9]inter	
[R9]interface g0/0/1
[R9-GigabitEthernet0/0/1]ip add	
[R9-GigabitEthernet0/0/1]ip address 192.168.30.2 24
[R9-GigabitEthernet0/0/1]
Apr  6 2021 16:57:22-08:00 R9 %%01IFNET/4/LINK_STATE(l)[1]:The line protocol IP 
on the interface GigabitEthernet0/0/1 has entered the UP state. 
[R9-GigabitEthernet0/0/1]q
[R9]ip	
[R9]ip tpu	
[R9]ip rou	
[R9]ip route-static 192.168.10.0 24 192.168.50.2
[R9]ip route-static 192.168.20.0 24 192.168.50.2
[R9]
[R9]ip route-static 192.168.20.0 24 192.168.50.2

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