Module 6 Review Questions

Front

Refer to the exhibit. What has to be done in order to complete the static NAT configuration on R1? Options: R1 should be configured with the command ip nat inside source static 209.165.200.1 192.168.11.11, R1 should be configured with the command ip nat inside source static 209.165.200.200 192.168.11.11, Interface S0/0/0 should be configured with the command ip nat outside, Interface Fa0/0 should be configured with the command no ip nat inside.

Back

Interface S0/0/0 should be configured with the command ip nat outside.

Answer explanation

In order for NAT translations to work properly, both an inside and outside interface must be configured for NAT translation on the router.

Front

Refer to the exhibit. A network administrator has configured R2 for PAT. Why is the configuration incorrect?

Back

NAT-POOL2 is bound to the wrong ACL.

Answer explanation

In the exhibit, NAT-POOL 2 is bound to ACL 100, but it should be bound to the configured ACL 1. This will cause PAT to fail. 100, but it should be bound to the configured ACL 1. This will cause PAT to fail.

Front

From the perspective of R1, the NAT router, which address is the inside global address?

Back

209.165.200.225

Answer explanation

There are four types of addresses in NAT terminology. Inside local address Inside global address Outside local address Outside global address The inside global address of PC1 is the address that the ISP sees as the source address of packets, which in this example is the IP address on the serial interface of R1, 209.165.200.224.

Front

Refer to the exhibit. Given the commands as shown, how many hosts on the internal LAN off R1 can have simultaneous NAT translations on R1?

Back

1

Answer explanation

The NAT configuration on R1 is static NAT which translates a single inside IP address, 192.168.0.10 into a single public IP address, 209.165.200.255. If more hosts need translation, then a NAT pool of inside global address or overloading should be configured.

Front

What is a disadvantage when both sides of a communication use PAT?

Back

End-to-end IPv4 traceability is lost.

Answer explanation

With the use of NAT, especially PAT, end-to-end traceability is lost. This is because the host IP address in the packets during a communication is translated when it leaves and enters the network. With the use of NAT/PAT, both the flexibility of connections to the Internet and security are actually enhanced. Host IPv4 addressing is provided by DHCP and not related to NAT/PAT.

Front

What IPv4 address is the source IP address in the packet between RT2 and the web server? Options: 192.0.2.2, 203.0.113.10, 172.16.1.254, 192.168.1.5, 209.165.200.245

Back

209.165.200.245

Answer explanation

Because the packet is between RT2 and the web server, the source IP address is the inside global address of PC, 209.165.200.245.

Front

Refer to the exhibit. Based on the output that is shown, what type of NAT has been implemented?

Back

PAT using an external interface

Answer explanation

The output shows that there are two inside global addresses that are the same but that have different port numbers. The only time port numbers are displayed is when PAT is being used. The same output would be indicative of PAT that uses an address pool. PAT with an address pool is appropriate when more than 4,000 simultaneous translations are needed by the company.

Front

In NAT terms, what address type refers to the globally routable IPv4 address of a destination host on the Internet?

Back

outside global

Answer explanation

From the perspective of a NAT device, inside global addresses are used by external users to reach internal hosts. Inside local addresses are the addresses assigned to internal hosts. Outside global addresses are the addresses of destinations on the external network. Outside local addresses are the actual private addresses of destination hosts behind other NAT devices.

Front

From the perspective of users behind the NAT router, what type of NAT address is 209.165.201.1?

Back

inside global

Answer explanation

From the perspective of users behind NAT, inside global addresses are used by external users to reach internal hosts. Inside local addresses are the addresses assigned to internal hosts. Outside global addresses are the addresses of destinations on the external network. Outside local addresses are the actual private addresses of destination hosts behind other NAT devices.

Front

What is the purpose of the overload keyword in the ip nat inside source list 1 pool NAT_POOL overload command?

Back

It allows many inside hosts to share one or a few inside global addresses.

Answer explanation

Dynamic NAT uses a pool of inside global addresses that are assigned to outgoing sessions. If there are more internal hosts than public addresses in the pool, then an administrator can enable port address translation with the addition of the overload keyword. With port address translation, many internal hosts can share a single inside global address because the NAT device will track the individual sessions by Layer 4 port number.