Cisco NAT - Overload PAT and Static nat from one inside to two outside interfaces

Question

i have following setup

Cisco ISR4k Router with one inside LAN interface and two outside Interfaces.

                          ---- WAN1 (NAT outside)
LAN (NAT inside) -- ISR4k |
                          ---- WAN2 (NAT outside)

There is just one single host in the LAN Network.

WAN1 is a network which is under my control. This is a public accessible /24 Network and i like to assign static 1:1 NAT to make the host in LAN reachable from the WAN1 outside network. This task is simple:

ip nat inside source static <inside local ip> <inside global ip>

WAN1 is the default gateway for this router and this works as expected.

WAN2 is a network out of my control. My router gets a random IPv4 address via the ISPs DHCP server on this interface. Host in LAN has to access specific targets exclusicely via WAN2 interface. So i configured some more specific routes and configured an overload NAT where these destination hosts are defined by an extended ACL.

ìp nat inside source list <ACL> interface <WAN2-interface> overload

But this doesnt work.

As long as the static NAT is configured "show ip nat translations" only displays the static NAT translation. No dynamic NAT entry is allocated. As soon as i remove the static NAT, the overload NAT stared to work immediately. So i can currently only have one working NAT translation.

any suggestions how to solve this?

Answer 1

As per your requirement your want to access both ISps access from your internet lan for this requirement please make changes as dynamic nat overload configured with both ISPs and configure two defaults routes pointing towards ISP gàteways . Please find below confirmation

#access-list permit 100 ip 192.168.10.5 255.255.255.255`

"Assuming your internal lan ip address is 192.168.10.5*

#ip nat inside souce list 100 interfàce wan1 overload

#ip nat inside source list 100 interfàce wan2 overload

IP route 0.0.0.0 0.0.0.0 point towards wan1 gateway

ip route 0.0.0.0 0.0.0.0 pointing towards wan2 gateway

Please try above configure to ensure load balancing between two ISPs