How to configure Cisco router for dual ISP with ISP1 primary and ISP2 backup

Описание: Hello everyone!

Today we can learn how to configure Cisco router for dual ISP with ISP1 primary and ISP2 backup.

We have ip address 100.100.100.2/30 on interface FastEthernet0/0 to ISP1

and ip address 200.200.200.2/30 on interface FastEthernet0/1 to ISP2.

Local network with 192.168.1.0/24 subnet connecting to GigabitEthernet1/0 interface of router.

For the local network running DHCP server on Cisco router. (DHCP preconfigured)

Remote server for checking has ip address 5.5.5.5

So let's go!

1. Router#configure terminal

Router(config)#interface gigabitethernet1/0

Router(config-if)#ip address 192.168.1.1 255.255.255.0

Router(config-if)#ip nat inside

Router(config-if)#no shutdown

Router(config-if)#exit

Router(config)#interface fastethernet0/0

Router(config-if)#ip address 100.100.100.2 255.255.255.252

Router(config-if)#ip nat outside

Router(config-if)#no shutdown

Router(config-if)#exit

Router(config)#interface fastethernet0/1

Router(config-if)#ip address 200.200.200.2 255.255.255.252

Router(config-if)#ip nat outside

Router(config-if)#no shutdown

Router(config-if)#exit

2. Router(config)#route-map FOR_ISP1 permit 10 --this route-maps define interface for particular ISP

Router(config-route-map)#match interface fastethernet 0/0

Router(config-route-map)#exit

Router(config)#route-map FOR_ISP2 permit 10

Router(config-route-map)#match interface fastethernet 0/1

Router(config-route-map)#exit

3. Router(config)#ip sla 10

Router(config-ip-sla)#icmp-echo 5.5.5.5 source ip 100.100.100.2 --it's pings for checking reachability ISP1

Router(config-ip-sla-echo)#frequency 10 --define interval of pings

Router(config-ip-sla-echo)#exit

Router(config)#ip sla schedule 10 start-time now life forever --it starts our sla now and will be running forever

Router(config)#track 1 ip sla 10 --starting tracking of our sla 10

Router(config-track)#delay up 10 down 10 --timeout intervals for tracking

Router(config-track)#exit

4. Router(config)#ip route 0.0.0.0 0.0.0.0 100.100.100.1 track 1 --this route will be in route table when ip sla is working

Router(config)#ip route 0.0.0.0 0.0.0.0 200.200.200.1 2 --this route when ISP1 is unreachable

5. Router(config)#ip nat inside source route-map FOR_ISP1 interface FastEthernet0/0 overload

Router(config)#ip nat inside source route-map FOR_ISP2 interface FastEthernet0/1 overload

Router(config)#ip nat translation timeout 10 -- clearing nat translation table in 10 seconds

Router(config)#end

Router#write

Thank you. See you around.