Explanation/Reference:
Explanation:
If all users cannot access the Internet, then R1 is most likely to cause the problem so we should check it first. From the "show running-config" command we will see:

Here we see that interface E0/0 (connected to ISP) has been configured as "nat inside" while interfaces E0/1 & E0/2 (connected to our company) have been configured as "nat outside". This is not correct because "nat inside" should be configured with interfaces connected to our company while "nat outside" should be configured with interfaces connected to the internet. Therefore, we can conclude the NAT configuration on these interfaces is not correct.