Google :
==============================================
!
hostname Google
!
!
interface Loopback0
 ip address 8.8.8.8 255.255.255.255
interface Ethernet0/1
 ip address 10.10.10.1 255.255.255.252
 ip ospf network point-to-point
!
interface Ethernet0/2
 ip address 10.10.20.1 255.255.255.252
 ip ospf network point-to-point
!
!
router ospf 1
 no auto-cost
 passive-interface default
 no passive-interface Ethernet0/1
 no passive-interface Ethernet0/2
 network 8.8.8.8 0.0.0.0 area 0
 network 10.10.10.0 0.0.0.3 area 0
 network 10.10.20.0 0.0.0.3 area 0
!
end


ISP1 :
==============================================
!
interface Ethernet0/0
 ip address 172.16.10.1 255.255.255.252
 ip ospf network point-to-point
!
interface Ethernet0/1
 ip address 10.10.10.2 255.255.255.252
 ip ospf network point-to-point
!
!
router ospf 1
 redistribute connected subnets
 passive-interface default
 no passive-interface Ethernet0/0
 no passive-interface Ethernet0/1
 network 10.10.10.0 0.0.0.3 area 0
 network 172.16.10.0 0.0.0.3 area 0
!

ISP2 :
==============================================

!
hostname ISP2
!
!
interface Ethernet0/0
 ip address 172.16.20.1 255.255.255.252
 ip ospf network point-to-point
!
interface Ethernet0/2
 ip address 10.10.20.2 255.255.255.252
 ip ospf network point-to-point
!
!
router ospf 1
 redistribute connected subnets
 passive-interface default
 no passive-interface Ethernet0/0
 no passive-interface Ethernet0/2
 network 10.10.20.0 0.0.0.3 area 0
 network 172.16.20.0 0.0.0.3 area 0
!
no ip http server
no ip http secure-server
ip route 192.168.20.0 255.255.255.252 172.16.20.2
!
!
end


GW1
==============================================
!
hostname GW1
!
!
interface Ethernet0/0
 ip address 172.16.10.2 255.255.255.252
 ip ospf network point-to-point
!
interface Ethernet0/1
 ip address 192.168.10.1 255.255.255.252
!
!
router ospf 1
 passive-interface default
 no passive-interface Ethernet0/0
 network 172.16.10.0 0.0.0.3 area 0
 network 192.168.10.0 0.0.0.3 area 1
!
no ip http server
no ip http secure-server
ip route 192.168.100.0 255.255.255.0 192.168.10.2
!
!
end


GW2
==============================================
!
interface Ethernet0/0
 ip address 172.16.20.2 255.255.255.252
 ip ospf network point-to-point
!
interface Ethernet0/2
 ip address 192.168.20.1 255.255.255.252
!
!
router ospf 1
 passive-interface default
 no passive-interface Ethernet0/0
 network 172.16.20.0 0.0.0.3 area 0
 network 192.168.20.0 0.0.0.3 area 1
!
!
no ip http server
no ip http secure-server
ip route 192.168.100.0 255.255.255.0 192.168.20.2
!
end


HOME#
===============
!
track 100 ip sla 1 reachability
!
ip tcp synwait-time 5
!
!
interface Ethernet0/0
 ip address 192.168.100.1 255.255.255.0
 ip nat inside
 ip virtual-reassembly in
!
interface Ethernet0/1
 ip address 192.168.10.2 255.255.255.252
 ip nat outside
 ip virtual-reassembly in
!
interface Ethernet0/2
 ip address 192.168.20.2 255.255.255.252
 ip nat outside
 ip virtual-reassembly in
!
!
no ip http server
no ip http secure-server
ip nat inside source route-map ISP1 interface Ethernet0/1 overload
ip nat inside source route-map ISP2 interface Ethernet0/2 overload
ip route 0.0.0.0 0.0.0.0 192.168.10.1 track 100
ip route 0.0.0.0 0.0.0.0 192.168.20.1 100
!
ip sla 1
 icmp-echo 8.8.8.8 source-interface Ethernet0/1
 frequency 5
ip sla schedule 1 life forever start-time now
!
route-map ISP2 permit 10
 match ip address 110
 match interface Ethernet0/2
!
route-map ISP1 permit 10
 match ip address 110
 match interface Ethernet0/1
!
!
access-list 110 permit ip 192.168.100.0 0.0.0.255 any
!
end