Floating routing
- Floating routing is also called routing backup
- Two or more links form a floating route
- Same destination address, different next hop address, another next hop has low priority
- The lower the administrative distance of the routing table, the higher the priority. For a simple example of floating routes, for example, change the priority of the management distance of dynamic routes to low, and change the priority of manually added static routes to high. When there is a problem with dynamic routing, the original routing will be invalid, and the router will automatically select a static route to ensure that the network is not interrupted and achieve redundant backup!
Experimental topology
The configuration commands are as follows:
- As shown in the topology diagram of the two PCs, add IP addresses and masks and gateways to them
- Note: After the PC is activated, it may also be down. The solution is to reconnect or reconnect a PC.
The PCA
PCB is
configured with the IP and mask and the gateway is enabled after the point, make sure that the status is UP
Router RA
<H3C>sys
[H3C]interface GigabitEthernet0/0
[H3C]ip address 192.168.0.1 255.255.255.0
[H3C]interface GigabitEthernet0/1
[H3C]ip address 192.168.1.1 255.255.255.252
[H3C]interface Serial1/0
[H3C]ip address 192.168.1.5 255.255.255.252
[H3C]rip
[H3C-rip-1]network 192.168.0.0
[H3C-rip-1]network 192.168.1.0
[H3C-rip-1]version 2
[H3C-rip-1]undo summary
[H3C-rip-1]silent-interface s 1/0
[H3C-rip-1]qu
[H3C]ip route-static 192.168.2.0 255.255.255.0 s 1/0 preference 120
Router RB
<H3C>sys
[H3C]interface Serial1/0
[H3C]ip address 192.168.1.6 255.255.255.252
[H3C]interface GigabitEthernet0/0
[H3C]ip address 192.168.2.1 255.255.255.0
[H3C]interface GigabitEthernet0/1
[H3C]ip address 192.168.1.2 255.255.255.252
[H3C]rip
[H3C-rip-1]network 192.168.1.0
[H3C-rip-1]network 192.168.2.0
[H3C-rip-1]version 2
[H3C-rip-1]undo summary
[H3C-rip-1]silent-interface s 1/0
[H3C-rip-1]qu
[H3C]ip route-static 192.168.0.0 255.255.255.0 s1/0 preference 120
Use display ip routing-table to check whether the RIP route is written. If it is written, in this case, save the router (save) and then reboot (reboot). Make sure that both routers have this route information. 
How to verify whether a floating route can be successfully enabled after a link is broken.
Hit the command on any router to close the port GE0 / 1
[H3C]interface GigabitEthernet 0/1
[H3C-GigabitEthernet0/1]shutdown
After closing, use display ip routing-table to check that
we can find that the RIP route is no longer there, and it has become our priority route 120. If we can successfully enable another route, the experiment is successful .
