Here is example : (take backup of config working one, understand the below config and apply as per the directions).
- configure interface
interface Gi0/1
description ISP1
ip address x.x.x.x 255.255.255.0 <- change as per the ISP1 IP address)
ip nat outside
interface Gi0/2
description ISP2
ip address y.y.y.y 255.255.255.0 <- change as per the ISP2 IP address)
ip nat outside
- Route Maps for NATting traffic
route-map backup permit 20
match ip address ISPInternet
match interface Gi0/2
route-map primary permit 10
match ip address ISPInternet
match interface Gi0/1
- Configure Lan interface
interface VLAN2
ip address z.z.z.z 255.255.255.0
ip nat inside
interface VLAN3
ip address z1.z1.z1.z1 255.255.255.0
ip nat inside
ip access-list extended ISPInternet
permit ip any any
- Configure the two NAT statements
ip nat inside source route-map backup interface Gi0/1 overload
ip nat inside source route-map primary interface Gi0/2 overload
- your static routes:
ip route 0.0.0.0 0.0.0.0 x.x.x.x 10
ip route 0.0.0.0 0.0.0.0 y.y.y.y 20
EEM Script to Clear the NAT :
event manager applet CLEARNAT1
event syslog pattern “LINEPROTO-5-UPDOWN: Line protocol on Interface Gi0/2, changed state to down”
action 1.0 cli command “enable”
action 2.0 cli command “clear ip nat translation *”
event manager applet CLEARNAT2
event syslog pattern “LINEPROTO-5-UPDOWN: Line protocol on Interface Gi0/1, changed state to down”
action 1.0 cli command “enable”
action 2.0 cli command “clear ip nat translation *”
Other Option with IP SLA Tracking :
ip sla 20
icmp-echo 8.8.8.8 source-interface Gi0/1
timeout 1000
frequency 10
ip sla schedule 20 life forever start-time now
track 1 rtr 20 reachability
- your static routes:
ip route 0.0.0.0 0.0.0.0 x.x.x.x track 1
ip route 0.0.0.0 0.0.0.0 y.y.y.y 2
