2020-06-18

Configure Dual ISP Failover in Cisco



1. Configure the first router for your first ISP.

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#ip route 0.0.0.0 0.0.0.0 10.0.10.1
Router(config)#exit

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int fastEthernet 2/0
Router(config-if)#description WAN
Router(config-if)#ip address 10.0.10.2 255.255.255.0
Router(config-if)#ip nat outside
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#exit
Router#copy run start
Destination filename [startup-config]?
Building configuration...
[OK]

Router(config)#int fa2/1
Router(config-if)#description LAN
Router(config-if)#no shutdown
Router(config-if)#ip address 192.168.1.1 255.255.0.0
Router(config-if)#ip nat inside
Router(config-if)#standby 1 ip 192.168.1.3
Router(config-if)#standby 1 priority 105
Router(config-if)#standby 1 preempt
Router(config-if)#exit
Router(config)#exit

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#ip name-server 8.8.8.8
Router(config)#ip name-server 8.8.4.4
Router(config)#exit
Router#copy run start
Destination filename [startup-config]?
Building configuration...
[OK]

Router(config)#ip access-list standard LAN
Router(config-std-nacl)#permit 192.168.0.0 0.0.255.255
Router(config-std-nacl)#exit
Router(config)#ip nat inside source list LAN int fa2/0 overload
Router(config)#exit
Router#copy run start

2. Configure the second router for your second ISP.

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#ip route 0.0.0.0 0.0.0.0 10.0.11.1
Router(config)#exit

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int fa
Router(config)#int fastEthernet 2/0
Router(config-if)#description WAN
Router(config-if)#ip address 10.0.11.2 255.255.255.0
Router(config-if)#ip nat outside
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#exit
Router#copy run start
Destination filename [startup-config]?
Building configuration...
[OK]

Router(config)#int fa2/1
Router(config-if)#description LAN
Router(config-if)#no shutdown
Router(config-if)#ip address 192.168.1.1 255.255.0.0
Router(config-if)#ip nat inside
Router(config-if)#standby 1 ip 192.168.1.3
Router(config-if)#standby 1 preempt
Router(config-if)#exit
Router(config)#exit

Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#ip name-server 8.8.8.8
Router(config)#ip name-server 8.8.4.4
Router(config)#exit
Router#copy run start
Destination filename [startup-config]?
Building configuration...
[OK]

Router(config)#ip access-list standard LAN
Router(config-std-nacl)#permit 192.168.0.0 0.0.255.255
Router(config-std-nacl)#exit
Router(config)#ip nat inside source list LAN int fa2/0 overload
Router(config)#exit
Router#copy run start


3. Configure the IP address of the client pc.

IP address: 192.168.1.10
Subnet Mask: 255.255.0.0
Gateway: 192.168.1.3
DNS Server: 8.8.8.8

4. Connect the 2 network cables from your 2 routers into the switch.
    Try to type ping 8.8.8.8 on the command prompt on the computer that was
    connected to the switch. Then unplug the cable of your first router from the
    switch. The computer will be disconnected to the internet for few seconds.                                           It will automatically connect to your second ISP.
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