How to set the redundancy with 3 ISP ?

[msompong1]

Hi All,

I've the project to create the internet link for the critical application , The requirement is have 3 ISP redundant following 

with the below picture.

- In normal situation the the traffic from PRD will connect internet with route1

- If route1 down will switch to route2

- If route1 and route2 down will switch to route3 

- If the primary route (route1) come UP the traffic will switch back.

I'm not so sure what is the method or technology in Cisco router can apply to this requirement.

Please kindly advice.

[Georg Pauwen]

Hello,

you could use multiple IP SLAs and tracking, which will do exactly what you want. Below is a sample config; if you cannot apply that to your router, post the running config...

track 1 ip sla 1 reachability
!
track 2 ip sla 2 reachability
!
track 3 list boolean or
object 1
object 2
!
interface FastEthernet0/0
description ISP Primary
ip address 100.100.100.1 255.255.255.252
duplex auto
speed auto
media-type rj45
!
interface FastEthernet0/1
description ISP Secondary
ip address 150.150.150.1 255.255.255.252
duplex auto
speed auto
media-type rj45
!
interface FastEthernet0/2
ip address 200.200.200.1 255.255.255.252
description ISP Terciary
duplex auto
speed auto
media-type rj45
!
ip route 0.0.0.0 0.0.0.0 100.100.100.2 track 1
ip route 0.0.0.0 0.0.0.0 150.150.150.2 100 track 2
ip route 0.0.0.0 0.0.0.0 200.200.2000.2 200
ip route 8.8.8.8 255.255.255.255 FastEthernet0/0
ip route 8.8.4.4 255.255.255.255 FastEthernet0/1
!
ip sla 1
icmp-echo 8.8.8.8 source-interface FastEthernet0/0
threshold 1000
timeout 3000
frequency 3

!
ip sla schedule 1 life forever start-time now

!
ip sla 2
icmp-echo 8.8.4.4 source-interface FastEthernet0/1
threshold 1000
timeout 3000
frequency 3

!
ip sla schedule 2 life forever start-time now
!
event manager applet CLEAR_NAT
event track 3 state any
action 1.0 cli command “enable”
action 2.0 cli command “clear ip nat translation *”
action 3.0 cli command "end"