Exam 200-310 topic 2 question 195 discussion

Actual exam question from Cisco's 200-310

Question #: 195
Topic #: 2

Your supervisor wants you to reduce the range of IP addresses available from a NAT pool that is configured on the department router. You should do this by enabling internal hosts to share a single external IP address.
Which of the following should you configure on RouterA?

A. NAT overloading
B. NAT overlapping
C. static NAT
D. dynamic NAT

Show Suggested Answer

Suggested Answer: A 🗳️
Section: Addressing and Routing Protocols in an Existing Network Explanation

You should configure Network Address Translation (NAT) overloading on RouterA to enable internal hosts to share a single external IP address. NAT overloading appends port numbers to IP addresses to enable multiple internal hosts to share the same external IP address. You can issue the ip nat inside source list access- list interface outside-interface overload command to configure NAT overloading with a single inside global address, or you can issue the ip nat inside source list access-list pool nat-pool overload command to configure NAT overloading with a NAT pool.
You do not need to configure dynamic NAT, because the network in this scenario already uses dynamic NAT. Dynamic NAT translates inside local addresses to inside global addresses; inside global addresses are allocated from a pool. To create a NAT pool, you should issue the ip nat pool nat-pool start-ip end-ip
{netmask mask | prefix-length prefix} command. To enable translation of inside local addresses, you should issue the ip nat inside source-list access-list pool nat- pool [overload] command.
You do not need to configure static NAT. Static NAT translates a single inside local address to a single inside global address, or a single outside local address to a single outside global address. You can configure a static inside local-to-inside global IP address translation by issuing the ip nat inside source static inside-local inside-global command. To configure a static outside local-to-outside global IP address translation, you should issue the ip nat outside source static outside-global outside-local command. Unlike dynamic NAT configurations, which are created in the NAT table when traffic is generated, static NAT configurations are always contained in the NAT table.
When a NAT router receives an Internet-bound packet from a local host, the NAT router performs the following tasks:
✑ It checks the static NAT mappings to verify whether an inside global address mapping exists for the localhost.
✑ If no static mapping exists, it dynamically maps the inside local address to an unused inside global-address, if one is available, from the NAT pool.
It changes the inside local address in the packet header to the inside global address and forwards the-packet to its destination:

When all the inside global addresses in the NAT pool are mapped, no other inside local hosts will be able to communicate on the Internet unless NAT overloading, also known as Port Address Translation (PAT), is configured. When NAT overloading is configured, an inside local address, along with a port number, is mapped to an inside global address. The NAT router uses port numbers to keep track of which packets belong to each host:

You do not need to configure NAT overlapping. You should use NAT overlapping when the addresses on the internal network conflict with the addresses on another network. The internal addresses must be translated to unique addresses on the external network, and addresses on the external network must be translated to unique addresses on the internal network; the translation can be performed either through static or dynamic NAT. Nothing in this scenario indicates that you are configuring the router for NAT overlapping.
Reference:
Cisco: Configuring Network Address Translation: Getting Started: Example: Allowing Internal Users to Access the Internet
Cisco: Configuring Network Address Translation: Getting Started

by [deleted] at April 3, 2025, 1:41 a.m.

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