How to configure floating routing?

[[416937]]

Experimental requirements

ISP-1 and ISP-2 use the same loopback port address. By changing the administrative distance of the GW default route, the GW can select the default route with a smaller administrative distance as the primary route and the default route with a larger administrative distance as the backup route, so as to achieve the purpose of selecting the best route for data communication.

IP Address Table

Experimental Configuration

as follows

Configure ISP-1:

 ISP-1(config)#interface f0/0
 ISP-1(config-if)#ipaddress 192.168.1.1 255.255.255.0 ISP-1(config-if)#noshutdown
 ISP-1(config-if)#exit
 ISP-1(config)#interface loopback 0
 ISP-1(config-if)#ipaddress 123.1.1.1 255.255.255.0 ISP-1(config-if)#exit

Configure ISP-2:

 ISP-2(config)#interfacef0/0
 ISP-2(config-if)#ipaddress192.168.2.2 255.255.255.0
 ISP-2(config-if)#noshutdown
 ISP-2(config-if)#exit
 ISP-2(config)#interfaceloopback0
 ISP-2(config-if)#ipaddress 123.1.1.1 255.255.255.0 ISP-2(config-if)#exit

Configure GW:

 GW(config)#interface f1/0
 GW(config-if)#ipaddress 192.168.1.2 255.255.255.0
 GW(config-if)#noshutdown
 GW(config-if)#exit
 GW(config)#interface f0/0
 GW(config-if)#ipaddress 192.168.2.1 255.255.255.0
 GW(config-if)#noshutdown
 GW(config-if)#exit
 GW(config)#iproute 123.1.1.1 255.255.255.255192.168.1.1 //

The line is the main line, the management distance is changed to 10, and this line is set as the backup line.

GW(config)#iproute 123.1.1.1 255.255.255.255192.168.2.2 10 //Set this line as the default route

Next: show iproute -----à Check the routing table. The GW shows that there are two links to the outgoing address 123.1.1.1, with administrative distances of 1 and 10 respectively.

Experimental Summary

When the administrative distance is not changed, the GW cannot reach the address 123.1.1.1. However, communication is possible by shutting down any interface on the GW.

After the administrative distance is changed, the GW will select the line with the smaller administrative distance as the primary line and communicate with the 123.1.1.1 address from the primary line.