HCNA Routing&Switching之静态路由
前文我们聊到了路由的相关概念和路由基础方面的话题，回顾请参考https://www.cnblogs.com/qiuhom-1874/p/14947897.html；今天我们聊聊静态路由相关话题；
回顾：在网络通信中，两个路由器要想通信，前提是必须有通往对端的路由；可以说路由是网络通信的基础条件；路由有很多种类，不同种类的路由信息其特点，优缺点各不相同；最为简单的就是直连路由，生成直连路由的必须满足两个条件，第一对应接口必须配置ip地址，其次对应接口物理和协议必须处于up状态；优点是自动生成，管理员只需要把对应接口配置上相应的地址，连上网线，对应直连路由就可以生成；缺点：只能够到达路由器直连的网络，不能够到达非直连的网络；
实验：如下图，配置好各设备的接口ip地址以后，看看对应路由表的变化，看看pc5,pc7以及R1是否能够ping同pc6?
分析：要想pc5,pc7和R1和pc6通信，首先R1要有去往pc6的路由，其次pc5和pc7的网关指向R1，因为pc6和pc5pc7不在同一网络（不在同一网络的设备通信，默认将数据包发送给网关）；
未配置R1各接口ip地址前的路由表
*down: administratively down
^down: standby
(l): loopback
(s): spoofing
The number of interface that is UP in Physical is 4
The number of interface that is DOWN in Physical is 0
The number of interface that is UP in Protocol is 1
The number of interface that is DOWN in Protocol is 3
Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 unassigned up down
GigabitEthernet0/0/1 unassigned up down
GigabitEthernet0/0/2 unassigned up down
NULL0 unassigned up up(s)
Route Flags: R - relay, D - download to fib
Routing Tables: Public
Destinations : 4 Routes : 4
Destination/Mask Proto Pre Cost Flags NextHop Interface
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0 127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
提示：可以看到在未配置接口ip地址前，查看路由表，路由表中只有回环接口的路由信息；查看接口简要信息也可以发现对应接口的物理状态是up的，协议状态是down，不满足生成直连路由的条件，所以路由表没有对应接口的路由信息；
配置R1
Enter system view, return user view with Ctrl+Z.
[Huawei]sys R1
[R1]int g0/0/0
[R1-GigabitEthernet0/0/0]ip add 10.0.0.254 24
Jul 2 2021 23:00:05-08:00 R1 %%01IFNET/4/LINK_STATE(l)[0]:The line protocol IP on the interface GigabitEthernet0/0/0 has entered the UP state. int g0/0/1
[R1-GigabitEthernet0/0/0]
[R1-GigabitEthernet0/0/1]ip add 11.0.0.254 24
[R1-GigabitEthernet0/0/1]int g0/0/2
[R1-GigabitEthernet0/0/2]ip add 12.0.0.1 24
Jul 2 2021 23:00:05-08:00 R1 %%01IFNET/4/LINK_STATE(l)[1]:The line protocol IP on the interface GigabitEthernet0/0/1 has entered the UP state.
[R1-GigabitEthernet0/0/2]ip add 12.0.0.1 24
Jul 2 2021 23:00:07-08:00 R1 %%01IFNET/4/LINK_STATE(l)[2]:The line protocol IP on the interface GigabitEthernet0/0/2 has entered the UP state.
[R1-GigabitEthernet0/0/2]q
[R1]dis ip int b
*down: administratively down
^down: standby
(l): loopback
(s): spoofing
The number of interface that is UP in Physical is 4
The number of interface that is DOWN in Physical is 0
The number of interface that is UP in Protocol is 4
The number of interface that is DOWN in Protocol is 0
Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 10.0.0.254/24 up up
GigabitEthernet0/0/1 11.0.0.254/24 up up
GigabitEthernet0/0/2 12.0.0.1/24 up up
NULL0 unassigned up up(s)
[R1]dis ip rou
[R1]dis ip routing-table
Route Flags: R - relay, D - download to fib
Routing Tables: Public
Destinations : 13 Routes : 13
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.0/24 Direct 0 0 D 10.0.0.254 GigabitEthernet0/0/0
10.0.0.254/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
11.0.0.0/24 Direct 0 0 D 11.0.0.254 GigabitEthernet0/0/1
11.0.0.254/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
11.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
12.0.0.0/24 Direct 0 0 D 12.0.0.1 GigabitEthernet0/0/2
12.0.0.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/2
12.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/2
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0 127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R1]
提示：可以看到在r1上的各接口上正确的配置上ip地址信息以后，对应接口的协议状态就从down转变为up状态，同时路由表中也多了对应网络的路由信息；
配置R2
Enter system view, return user view with Ctrl+Z.
[Huawei]sys R2
[R2]int g0/0/0
[R2-GigabitEthernet0/0/0]ip add 12.0.0.2 24
[R2-GigabitEthernet0/0/0]int g0/0/1
Jul 2 2021 23:05:39-08:00 R2 %%01IFNET/4/LINK_STATE(l)[2]:The line protocol IP on the interface GigabitEthernet0/0/0 has entered the UP state.
[R2-GigabitEthernet0/0/0]int g0/0/1
[R2-GigabitEthernet0/0/1]ip add 22.0.0.254 24
Jul 2 2021 23:05:40-08:00 R2 %%01IFNET/4/LINK_STATE(l)[3]:The line protocol IP on the interface GigabitEthernet0/0/1 has entered the UP state.
[R2-GigabitEthernet0/0/1]q
[R2]dis ip int b
*down: administratively down
^down: standby
(l): loopback
(s): spoofing
The number of interface that is UP in Physical is 3
The number of interface that is DOWN in Physical is 1
The number of interface that is UP in Protocol is 3
The number of interface that is DOWN in Protocol is 1
Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 12.0.0.2/24 up up
GigabitEthernet0/0/1 22.0.0.254/24 up up
GigabitEthernet0/0/2 unassigned down down
NULL0 unassigned up up(s)
[R2]dis ip rout
[R2]dis ip routing-table
Route Flags: R - relay, D - download to fib
Routing Tables: Public
Destinations : 10 Routes : 10
Destination/Mask Proto Pre Cost Flags NextHop Interface
12.0.0.0/24 Direct 0 0 D 12.0.0.2 GigabitEthernet0/0/0
12.0.0.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
12.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
22.0.0.0/24 Direct 0 0 D 22.0.0.254 GigabitEthernet0/0/1
22.0.0.254/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
22.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0 127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R2]
提示：按照题意我们配置好了两个路由器的名称和相关接口的ip地址，对应路由器各自都生成了相应的直连路由；
配置好各pc的ip地址信息，然后用pc5ping pc6看看是否可以正常通信？
配置pc5
提示：pc5和R1的g0/0/0口是直连，所以对应pc5的网关必须指向R1的g0/0/0接口的ip地址；
配置pc6
提示：pc6和R2的g0/0/1口是直连，所以对应pc6的网关必须指向R2的g0/0/1接口的ip地址；
配置pc7
提示：pc7和R1的g0/0/1口是直连，所以对应pc7的网关必须指向R1的g0/0/1接口的ip地址；
验证：pc5 ping pc6看看是否可以通信？
PC>ipconfig
Link local IPv6 address………..: fe80::5689:98ff:fe54:5adc
IPv6 address………………….: :: / 128
IPv6 gateway………………….: ::
IPv4 address………………….: 10.0.0.1
Subnet mask…………………..: 255.255.255.0
Gateway………………………: 10.0.0.254
Physical address………………: 54-89-98-54-5A-DC
DNS server……………………:
PC>ping 22.0.0.1
Ping 22.0.0.1: 32 data bytes, Press Ctrl_C to break
Request timeout!
Request timeout!
Request timeout!
Request timeout!
Request timeout!
--- 22.0.0.1 ping statistics ---
5 packet(s) transmitted
0 packet(s) received
100.00% packet loss
PC>
提示：可以看到在pc5上ping pc6，给我们的回馈是请求超时；
在r1的g0/0/2口抓包，看看对应是否有数据包通过？
提示：可以看到在R1的g0/0/2口上没有抓到任何数据包，说明ping22.0.0.1的数据包没有在r1和r2直连链路上通过，所以我们ping pc6回馈给我们的是请求超时，其原因是R1上没有去往pc6的路由，当R1收到pc5发来的数据包，查看对应数据包是去往22.0.0.1的，R1在自己的路由表中没有匹配到去往22.0.0.1的路由，所以R1直接将对应数据包丢弃，不予转发；
验证：用pc5 ping pc7 看看是否能够正常通信？
PC>ipconfig
Link local IPv6 address………..: fe80::5689:98ff:fe54:5adc
IPv6 address………………….: :: / 128
IPv6 gateway………………….: ::
IPv4 address………………….: 10.0.0.1
Subnet mask…………………..: 255.255.255.0
Gateway………………………: 10.0.0.254
Physical address………………: 54-89-98-54-5A-DC
DNS server……………………:
PC>ping 11.0.0.1
Ping 11.0.0.1: 32 data bytes, Press Ctrl_C to break
Request timeout!
From 11.0.0.1: bytes=32 seq=2 ttl=127 time=16 ms
From 11.0.0.1: bytes=32 seq=3 ttl=127 time=16 ms
From 11.0.0.1: bytes=32 seq=4 ttl=127 time=16 ms
From 11.0.0.1: bytes=32 seq=5 ttl=127 time<1 ms
--- 11.0.0.1 ping statistics ---
5 packet(s) transmitted
4 packet(s) received
20.00% packet loss
round-trip min/avg/max = 0/12/16 ms
PC>
提示：可以看到pc5 是可以正常和pc7通信；其实原因很简单，就是因为R1上有对应去往pc7和pc5的直连路由，所以pc5和pc7可以正常通信；通过上述实验，可以看到直连路由的优点是它自动生成，只要管理员正确配置了ip地址，并且在接口上接上了线，对应直连路由就会自动生成了；缺点就是不能和非直连的网络通信；这样一来我们要想和非直连网络通信，光凭直连路由是做不到；
静态路由
所谓静态路由就是指管理员人工手动添加的路由信息；
添加静态路由的命令语法
ip route-static 目标网络 子网掩码/前缀 下一跳地址/出接口
提示：如果出接口为以太网接口，则必须要指定下一跳地址，如果出接口为串口，可以使用下一跳或出接口来配置；
实验：还是上面的top，实现pc5能够ping 通pc6
在R1上添加静态路由
验证：现在R1上有去往pc6的路由信息，用pc 5ping pc6 看看是否可以正常通信？
PC>ipconfig
Link local IPv6 address………..: fe80::5689:98ff:fe54:5adc
IPv6 address………………….: :: / 128
IPv6 gateway………………….: ::
IPv4 address………………….: 10.0.0.1
Subnet mask…………………..: 255.255.255.0
Gateway………………………: 10.0.0.254
Physical address………………: 54-89-98-54-5A-DC
DNS server……………………:
PC>ping 22.0.0.1
Ping 22.0.0.1: 32 data bytes, Press Ctrl_C to break
Request timeout!
Request timeout!
Request timeout!
Request timeout!
Request timeout!
--- 22.0.0.1 ping statistics ---
5 packet(s) transmitted
0 packet(s) received
100.00% packet loss
PC>
提示：可以看到pc5现在依然ping 不通pc6；
在r1的g0/0/2口抓包，看看是否有对应数据包通过？
提示：现在在R1的g0/0/2口可以抓到pc5 ping pc 6的包，但是没有pc6 回来的包，其原因是R2上没有到达pc5所在网络的路由；所以pc5 ping 不同pc6;
在R2上添加去往pc5的路由
验证：现在用pc5再次ping pc6看看是否能通？
PC>ipconfig
Link local IPv6 address………..: fe80::5689:98ff:fe54:5adc
IPv6 address………………….: :: / 128
IPv6 gateway………………….: ::
IPv4 address………………….: 10.0.0.1
Subnet mask…………………..: 255.255.255.0
Gateway………………………: 10.0.0.254
Physical address………………: 54-89-98-54-5A-DC
DNS server……………………:
PC>ping 22.0.0.1
Ping 22.0.0.1: 32 data bytes, Press Ctrl_C to break
Request timeout!
From 22.0.0.1: bytes=32 seq=2 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=3 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=4 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=5 ttl=126 time=16 ms
--- 22.0.0.1 ping statistics ---
5 packet(s) transmitted
4 packet(s) received
20.00% packet loss
round-trip min/avg/max = 0/16/16 ms
PC>
提示：可以看到pc5可以正常ping 通pc6了；
验证：在R1的g0/0/2口抓包，看看对应数据包是否有回复了？
提示：可以看到现在在R1的g0/0/2口抓包就有正常回复包；
验证：pc7 ping pc6，看看是否能够ping通？
PC>ipconfig
Link local IPv6 address………..: fe80::5689:98ff:fe99:6332
IPv6 address………………….: :: / 128
IPv6 gateway………………….: ::
IPv4 address………………….: 11.0.0.1
Subnet mask…………………..: 255.255.255.0
Gateway………………………: 11.0.0.254
Physical address………………: 54-89-98-99-63-32
DNS server……………………:
PC>ping 22.0.0.1
Ping 22.0.0.1: 32 data bytes, Press Ctrl_C to break
Request timeout!
Request timeout!
Request timeout!
Request timeout!
Request timeout!
--- 22.0.0.1 ping statistics ---
5 packet(s) transmitted
0 packet(s) received
100.00% packet loss
PC>
提示：可以看到pc7到现在依然无法Ping通pc6,其原因是r2没有回来pc7的路由，所以pc7现在能够把包送达到pc6，但回不来，所以导致pc7ping不同pc6;要想实现pc7ping通pc6,我们还需要在r2上添加一条去往pc7的路由；
在R2上添加去往pc7的路由
验证：现在pc7 ping pc6，看看是否可以正常通信？
PC>ipconfig
Link local IPv6 address………..: fe80::5689:98ff:fe99:6332
IPv6 address………………….: :: / 128
IPv6 gateway………………….: ::
IPv4 address………………….: 11.0.0.1
Subnet mask…………………..: 255.255.255.0
Gateway………………………: 11.0.0.254
Physical address………………: 54-89-98-99-63-32
DNS server……………………:
PC>ping 22.0.0.1
Ping 22.0.0.1: 32 data bytes, Press Ctrl_C to break
From 22.0.0.1: bytes=32 seq=1 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=2 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=3 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=4 ttl=126 time=16 ms
From 22.0.0.1: bytes=32 seq=5 ttl=126 time=16 ms
--- 22.0.0.1 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 16/16/16 ms
PC>
提示：可以看到pc7现在也能正常ping通pc6;通过上述实验我们发现静态路由的配置还是很简单，必须手动指定目标网络，掩码以及下一跳；其次网络通信的过程是是双向的，配置静态路由，我们必须考虑来回的路由在所经过的路由器都要有对应的路由；如果网络规模非常大（网段特别多，路由器特别多），如果用手动配置静态路由的方式，就不是很容易了；所以静态路由适用于网络规模不是太大的环境中；除此之外静态路由有一个非常大的缺点，它不能根据top变化而变化，这样一来，如果现网中某个接口地址的发生变化，管理员必须手动更改路由信息；
负载分担
负载分担就是等价路由即到达同一目标网络的路由有多条，并且他们的优先级开销都一样；
实验：如下图，配置pc5和pc6通信的流量都可以走R1,R2之间的两条链路
在R1的g0/0/1接口上配置对应的ip地址，并配置访问pc6的对应路由信息
Enter system view, return user view with Ctrl+Z.
[R1]int g0/0/1
[R1-GigabitEthernet0/0/1]ip add 21.0.0.1 24
[R1-GigabitEthernet0/0/1]q
[R1]ip route-s 22.0.0.1 32 21.0.0.2
[R1]dis ip routin
[R1]dis ip routing-table
Route Flags: R - relay, D - download to fib
Routing Tables: Public
Destinations : 14 Routes : 15
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.0/24 Direct 0 0 D 10.0.0.254 GigabitEthernet0/0/0
10.0.0.254/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
12.0.0.0/24 Direct 0 0 D 12.0.0.1 GigabitEthernet0/0/2
12.0.0.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/2
12.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/2
21.0.0.0/24 Direct 0 0 D 21.0.0.1 GigabitEthernet0/0/1
21.0.0.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
21.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
22.0.0.1/32 Static 60 0 RD 12.0.0.2 GigabitEthernet0/0/2
Static 60 0 RD 21.0.0.2 GigabitEthernet0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0 127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R1]
在R2的g0/0/2接口上配置对应的ip地址，并配置访问pc5的对应路由信息
Enter system view, return user view with Ctrl+Z.
[R2]int g0/0/2
[R2-GigabitEthernet0/0/2]ip add 21.0.0.2 24
Jul 3 2021 00:34:04-08:00 R2 %%01IFNET/4/LINK_STATE(l)[0]:The line protocol IP on the interface GigabitEthernet0/0/2 has entered the UP state.
[R2-GigabitEthernet0/0/2]q
[R2]ip route-s 10.0.0.1 32 21.0.0.1
[R2]dis ip routing
[R2]dis ip routing-table
Route Flags: R - relay, D - download to fib
Routing Tables: Public
Destinations : 15 Routes : 16
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.1/32 Static 60 0 RD 12.0.0.1 GigabitEthernet0/0/0
Static 60 0 RD 21.0.0.1 GigabitEthernet0/0/2
11.0.0.1/32 Static 60 0 RD 12.0.0.1 GigabitEthernet0/0/0
12.0.0.0/24 Direct 0 0 D 12.0.0.2 GigabitEthernet0/0/0
12.0.0.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
12.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
21.0.0.0/24 Direct 0 0 D 21.0.0.2 GigabitEthernet0/0/2
21.0.0.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/2
21.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/2
22.0.0.0/24 Direct 0 0 D 22.0.0.254 GigabitEthernet0/0/1
22.0.0.254/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
22.0.0.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0 127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
[R2]
提示：这样配置以后，pc5所在网络和pc6所在网络的设备通信就有两条链路一起负载，这样可以减少之前一条链路的压力；
验证：用tracert 追踪pc5和pc6通信所走的链路
提示：从上面的链路追踪和抓包可以看到现在pc5和pc6通信，两条链路都用上了，pc5pingpc6走下面21网段，回复包全部走12网段所在链路，pc6pingpc5 去走12网段所在链路，回来走21网段所在链路；
浮动路由
浮动路由又称主备路由，即去往同一网络的多条路由中有主备之分，默认情况主路由工作（活动路由），一旦活动路由宕掉，备份路由马上就变为活动路由；一旦主路由恢复，备份路由又会处于非活动状态；有点类似keepalived的抢占模式，一旦主挂了，备份路由马上变为主，一旦原来的主活了，现在的主马上就变为备份路由；其原理就是在等价路由的基础上，借助路由器转发原则根据其优先级来确定那条路由存在路由表（最优路由），一旦存在路由表中的最优路由链路宕掉，对应接口也会随之宕掉，所以对应最优路由来说，其出接口就会变为unknow状态，导致路由不可用，此时根据路由转发原则，原来的次优路由就会变为最优路由，一旦优先级最小的路由所在链路恢复正常，路由器又会根据路由转发原则把次优路由替换下来，让其处于非活动状态；
实验：还是上述top，在R1上配置12网段所在链路为主链路，21网段为备份链路
配置r1
[R1]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 1 Routes : 2 Configured Routes : 2
Static routing table status :
Destinations : 1 Routes : 2
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 60 0 RD 12.0.0.2 GigabitEthernet0/0/2
Static 60 0 RD 21.0.0.2 GigabitEthernet0/0/1Static routing table status :
Destinations : 0 Routes : 0
[R1]ip rou
[R1]ip route-s 22.0.0.1 32 21.0.0.2 pre 61
Info: Succeeded in modifying route.
[R1]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 1 Routes : 2 Configured Routes : 2
Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 60 0 RD 12.0.0.2 GigabitEthernet0/0/2Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 61 0 R 21.0.0.2 GigabitEthernet0/0/1[R1]
提示：在R1上修改原有去往22.0.0.1 下一跳为21.0.0.2 的路由的优先级为61，此时对应路由器来说，去往22.0.0.1的两条路由就不再是等价路由，所以下一跳为12.0.0.2的路由就会被选为最优路由，下一跳为21.0.0.2的路由就会被选为次优非活动路由；这里需要提醒的是以上路由只是针对r1，对r2来说，它的路由还是等价路由，并不会改变；
配置R2，12网段所在链路为备份链路，21网段为主链路
[R2]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 2 Routes : 3 Configured Routes : 3
Static routing table status :
Destinations : 2 Routes : 3
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.1/32 Static 60 0 RD 12.0.0.1 GigabitEthernet0/0/0
Static 60 0 RD 21.0.0.1 GigabitEthernet0/0/2
11.0.0.1/32 Static 60 0 RD 12.0.0.1 GigabitEthernet0/0/0Static routing table status :
Destinations : 0 Routes : 0
[R2]ip route-s 10.0.0.1 32 12.0.0.1 pre 61
Info: Succeeded in modifying route.
[R2]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 2 Routes : 3 Configured Routes : 3
Static routing table status :
Destinations : 2 Routes : 2
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.1/32 Static 60 0 RD 21.0.0.1 GigabitEthernet0/0/2
11.0.0.1/32 Static 60 0 RD 12.0.0.1 GigabitEthernet0/0/0Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.0.1/32 Static 61 0 R 12.0.0.1 GigabitEthernet0/0/0[R2]
验证：在R1上把12网段所在接口宕掉，看看对应的备份路由是否会成为活动路由？
Enter system view, return user view with Ctrl+Z.
[R1]dis ip int b
*down: administratively down
^down: standby
(l): loopback
(s): spoofing
The number of interface that is UP in Physical is 4
The number of interface that is DOWN in Physical is 0
The number of interface that is UP in Protocol is 4
The number of interface that is DOWN in Protocol is 0
Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 10.0.0.254/24 up up
GigabitEthernet0/0/1 21.0.0.1/24 up up
GigabitEthernet0/0/2 12.0.0.1/24 up up
NULL0 unassigned up up(s)
[R1]int g0/0/2
[R1-GigabitEthernet0/0/2]shutdow
Jul 3 2021 01:22:12-08:00 R1 %%01IFPDT/4/IF_STATE(l)[0]:Interface GigabitEthernet0/0/2 has turned into DOWN state.
[R1-GigabitEthernet0/0/2]
[R1-GigabitEthernet0/0/2]
Jul 3 2021 01:22:13-08:00 R1 %%01IFNET/4/LINK_STATE(l)[1]:The line protocol IP on the interface GigabitEthernet0/0/2 has entered the DOWN state.
[R1-GigabitEthernet0/0/2]q
[R1]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 1 Routes : 2 Configured Routes : 2
Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 61 0 RD 21.0.0.2 GigabitEthernet0/0/1Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 60 0 12.0.0.2 Unknown[R1]
提示：可以看到R1上的g0/0/2接口宕掉以后，对应活动路由变成了非活动路由，原来的非活动路由变成了活动路由；当然路由的变化也意味着其数据包的走向也发生了变化，从而实现链路切换；
恢复R1上的g0/0/2接口，看看对应路由变化
[R1-GigabitEthernet0/0/2]undo shutdown
[R1-GigabitEthernet0/0/2]
Jul 3 2021 01:26:52-08:00 R1 %%01IFPDT/4/IF_STATE(l)[2]:Interface GigabitEthernet0/0/2 has turned into UP state.
[R1-GigabitEthernet0/0/2]
Jul 3 2021 01:26:52-08:00 R1 %%01IFNET/4/LINK_STATE(l)[3]:The line protocol IP on the interface GigabitEthernet0/0/2 has entered the UP state.
[R1-GigabitEthernet0/0/2]q
[R1]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 1 Routes : 2 Configured Routes : 2
Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 60 0 RD 12.0.0.2 GigabitEthernet0/0/2Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
22.0.0.1/32 Static 61 0 R 21.0.0.2 GigabitEthernet0/0/1[R1]
提示：可以看到当接口恢复，对应活动路由又会变为非活动路由，实现了链路和路由的切换；当然对于r2也是同样的原理；从某种意义上我们可以理解浮动路由其实就是链接的高可用；
缺省路由
从上面的实验和配置过程来看，使用静态路由，必须在对应路由器上配置上数据包来回的路由，如果没有对应网段的路由，则我们就不能够正常访问对应的目标网络；这样一来我们如果要访问的网络非常多，比如互联网，我们不能也不应该把全互联网所有路由都写进路由器，即便可以，运营商和互联网的路由非常多，一般路由器也存不下，为了解决这样的问题，缺省路由就可以派上用场了；所谓缺省路由是指，在路由表中，所有未被匹配的路由，都可以被缺省路由所匹配；缺省路由以0.0.0.0为目标网络，掩码为0.0.0.0或前缀为0 来表示匹配任意目标网络；根据路由器的转发原则，掩码最长匹配优先，缺省路由的优先级是最低的，即最后才会被匹配；缺省路由的作用是减少路由条目，减轻路由器查找匹配路由的压力；通常用于末梢网络，比如家庭上网，企业出口；缺省路由可以静态配置，也可通过动态路由协议发布；
实验：静态配置缺省路由，实现pc5和pc6互通
配置R1
Enter system view, return user view with Ctrl+Z.
[Huawei]sys R1
[R1]int g0/0/0
[R1-GigabitEthernet0/0/0]ip add 10.0.0.254 24
[R1-GigabitEthernet0/0/0]int g0/0/1
[R1-GigabitEthernet0/0/1]ip add 12.0.0.1 24
Jul 3 2021 01:55:33-08:00 R1 %%01IFNET/4/LINK_STATE(l)[0]:The line protocol IP on the interface GigabitEthernet0/0/0 has entered the UP state.
[R1-GigabitEthernet0/0/1]ip add 12.0.0.1 24
[R1-GigabitEthernet0/0/1]q
[R1]ip route-s 0.0.0.0 0 12.0.0.2
Jul 3 2021 01:55:33-08:00 R1 %%01IFNET/4/LINK_STATE(l)[1]:The line protocol IP on the interface GigabitEthernet0/0/1 has entered the UP state.
[R1]ip route-s 0.0.0.0 0 12.0.0.2
[R1]dis ip routing-table pro static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 1 Routes : 1 Configured Routes : 1
Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 Static 60 0 RD 12.0.0.2 GigabitEthernet0/0/1Static routing table status :
Destinations : 0 Routes : 0
[R1]
配置R2
Enter system view, return user view with Ctrl+Z.
[Huawei]sys R2
[R2]int g0/0/0
[R2-GigabitEthernet0/0/0]ip add 12.0.0.2 24
[R2-GigabitEthernet0/0/0]int g0/0/1
[R2-GigabitEthernet0/0/1]ip add 22.0.0.254
Jul 3 2021 01:55:45-08:00 R2 %%01IFNET/4/LINK_STATE(l)[0]:The line protocol IP on the interface GigabitEthernet0/0/0 has entered the UP state.
[R2-GigabitEthernet0/0/1]ip add 22.0.0.254 24
[R2-GigabitEthernet0/0/1]q
[R2]ip route-s 0.0.0.0 0 12.0.0.1
Jul 3 2021 01:55:45-08:00 R2 %%01IFNET/4/LINK_STATE(l)[1]:The line protocol IP on the interface GigabitEthernet0/0/1 has entered the UP state.
[R2]ip route-s 0.0.0.0 0 12.0.0.1
[R2]dis ip routing-table protocol static
Route Flags: R - relay, D - download to fib
Public routing table : Static
Destinations : 1 Routes : 1 Configured Routes : 1
Static routing table status :
Destinations : 1 Routes : 1
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 Static 60 0 RD 12.0.0.1 GigabitEthernet0/0/0Static routing table status :
Destinations : 0 Routes : 0
[R2]
验证：用pc5 ping pc6 看看是否可以互通？
提示：可以看到配置缺省静态路由以后，pc5是可以正常和pc6通信；同样的原理，pc6也是可以正常和pc5通信；有了缺省路由我们只需要写一条了路由，即可匹配任意路由；这里需要提醒一下，缺省路由一般用于末梢网络，如果不是末梢网络的路由器，需要结合静态明细路由或动态路由；
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