ip nat outside source static 172.16.110.1 172.16.104.10
in which IP-CEF & IP-FASTSWITCHING are disabled to better understand debug messages related to IP routing & NAT processing
R4 is configured for "outside source static" translating and, as debug show, a ping packet entering from outside fast0/1 is translated (outside global -> ouside local) and then routed to ser0/0.234 outgoing i/f (inside i/f)
However pinging the remote loopabck router (184.108.40.206), attached on inside i/f, from 172.16.110.1, configured on a router attached on outside side, doesn't work !
Adding ip nat outside on loopback 104 i/f solve the issue; now debug shows
For outside static nat, you usually nat to an address that your router knows how to get to. The result that you got was because the address that you're natting to is on the loopback and not the f0/0 interface where I'm sure the traffic is coming from. You would need to put "ip nat outside" on the loopback interface in this scenario because you're telling the router that the address to use as outgoing nat is the loopback interface. Otherwise, you can nat to an address on your fa0/0 interface and your should be fine like:
ip nat outside source static 172.16.110.1 172.16.64.49
Then you'd be able to ping your loopback without putting a nat statement on the interface.
My conclusion is that without NAT enabled on that interface, the router looks in the local routing table for the destination of 220.127.116.11 and realizes that it's local to the router...dropping the traffic. With NAT enabled, it looks in the translation table to see what it's translated to and then routes to the translated address.
Pro Inside global Inside local Outside local Outside global
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