The last few weeks, this blog has included several topics outside the scope of CCNA, but I had promised to get back to a few of the most popular requested CCNA topics soon. This week, I’ll look at NAT/PAT again, and try to bump up the difficulty level. A few weeks ago, I posted some NAT comments about an ICND1/CCENT level NAT question, and this week I’ll try and use a question that’s more attuned to the ICND2 exam.
I’ll start today by posting something akin to an ICND2-level NAT exam question. In case you like timing yourself, and keeping to that 70 seconds/question goal that I mentioned in a posting a few months ago, get ready to time yourself.
By the way, please feel free to discuss your thoughts/ideas by adding to the blog. However, it’s better if you avoid posting your chosen answer(s) in the title of your post, just to prevent giving unwanted hints to others who are trying to first work on the problem themselves.
OK, here’s the question. Start your timer…
Router R1 was recently installed and configured to so that it could perform source NAT for all the private IP addresses in network 192.168.1.0/24. PC1 has failed to connect to web server S1, with PC1’s web browser simply timing out when trying to connect to 128.107.1.1. PC1 can ping 192.168.1.1, and R1 can successfully ping S1’s IP address (128.107.1.1). The following text shows all of R1’s configuration that could be related to the problem. Which of the following answers could be the root cause of this problem?
A) R1’s configuration uses a pool of IP addresses on the loopback interface’s subnet, which is not allowed
B) R1 is missing an overload parameter on the ip nat inside source command.
C) R1 is missing an ip nat outside command on interface S0/1/0
D) R1 is missing an ip nat outside command on interface loopback0
E) Router ISP1 does not have a route that matches the address range for subnet 192.31.7.0/28
F) Access-list 1 does not match PC1’s IP address
interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface Serial0/1/0
ip address 64.104.1.1 255.255.255.252
!
interface loopback0
ip address 192.31.7.1 255.255.255.240
!
ip nat pool fred 192.31.7.1 192.31.7.14 netmask 255.255.255.240
ip nat inside source list 1 pool fred
!
access-list 1 permit 192.168.1.0 0.0.0.255
Next entry, I’ll start breaking down this question.
