I have a 'simple' dual-homed ISP using two default-routes. Here's the sample config:
int s0
ip add 1.1.1.1 255.255.255.252
ip nat outside
!
int s0
ip add 2.2.2.1 255.255.255.252
ip nat outside
!
int f0
ip add 192.168.1.1 255.255.255.0
ip nat inside
!
ip nat pool isp1 1.1.1.1 1.1.1.1 netmask 255.255.255.252
ip nat pool isp2 2.2.2.1 2.2.2.1 netmask 255.255.255.252
ip nat inside source list LAN pool isp1 overload
ip nat inside source list LAN_ pool isp2 overload
!
ip access-list standard LAN
permit 192.168.1.0 0.0.0.255
!
ip access-list standard LAN_
permit 192.168.1.0 0.0.0.255
!
ip route 0.0.0.0 0.0.0.0 1.1.1.2
ip route 0.0.0.0 0.0.0.0 2.2.2.2
!
end
Using the config above, outbound traffic gets load-shared between the two ISPs if both links are up, which is desireable. But if we were to simulate a failure on ISP1 (ie. put Serial0 in admin down), the LAN users gets disconnected and will not use ISP2 unless we remove the ip nat entry for the ISP1. What am I missing?
All the end user wanted is the ability to load-balance between their two ISPs and failover to the other ISP if one fails.
