Cisco NAT Configuration Quiz

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Questions and Answers

What is the first step in configuring NAT with a specified pool on R2?

Set the netmask for the NAT pool

Configure the NAT pool (correct)

Assign the NAT pool to an interface

Define an access list for NAT

What occurs when PAT encounters two packets with the same source port from different hosts?

PAT assigns a new unique port to the second packet (correct)

Both packets are dropped

The packets are forwarded without modification

The first packet is modified with a lower priority

Which command correctly permits traffic from the specified network to use the defined NAT pool?

access-list 1 deny any

interface NAT-POOL2 ip nat inside

ip nat inside source list 1 pool NAT-POOL2 overload (correct)

permit ip any any

How does R2 modify the packets from PC1 before forwarding them to Svr1?

It alters the source IPv4 address to the inside global address Signup and view all the answers

What is the purpose of the command 'ip nat inside' on the interface serial0/1/0?

To designate the interface as a source for NAT translations Signup and view all the answers

What does IP NAT overload allow in a NAT configuration?

Multiple devices to share a single public IP address Signup and view all the answers

What is the significance of the netmask 255.255.255.224 in the NAT pool configuration?

It specifies the number of available public IP addresses in the pool Signup and view all the answers

During packet forwarding, which address does R2 use as the 'inside global address' for PC2?

209.165.200.225 Signup and view all the answers

What is a primary characteristic of Static NAT?

It maps local and global addresses in a one-to-one relationship. Signup and view all the answers

Which statement is true regarding Dynamic NAT?

It assigns public addresses on a first-come, first-served basis. Signup and view all the answers

How does Port Address Translation (PAT) identify specific NAT translations?

By utilizing the TCP port number for each session. Signup and view all the answers

What requirement must be fulfilled for both Static and Dynamic NAT operations?

Sufficient public addresses must be available for simultaneous sessions. Signup and view all the answers

What is the main advantage of using PAT in a network?

It minimizes the number of public IP addresses required. Signup and view all the answers

Which of the following best describes the process of packet forwarding in Static NAT?

Packets are forwarded consistently to their mapped public address. Signup and view all the answers

In which scenario is Dynamic NAT preferred over Static NAT?

When user sessions vary significantly in number. Signup and view all the answers

What disadvantage can arise from using PAT?

Potential for port number exhaustion with many devices. Signup and view all the answers

What is the primary purpose of the command 'ip nat pool NAT-POOL1 209.165.200.226 209.165.200.240 netmask 255.255.255.224'?

To specify a range of inside global addresses for NAT. Signup and view all the answers

Which command specifies that an interface is part of the inside network for NAT?

ip nat inside Signup and view all the answers

During the dynamic NAT process, what happens when R2 receives the first packet from PC1?

R2 creates a translation table entry and replaces the inside local address. Signup and view all the answers

What is required to allow PC1 and PC2's packets to be translated?

An access-list permitting their local addresses. Signup and view all the answers

What does the command 'access-list 1 permit 192.168.0.0 0.0.255.255' accomplish in this configuration?

It permits all addresses in the 192.168.0.0 range for NAT translation. Signup and view all the answers

When PC2 sends a packet after PC1, which global address will R2 assign to PC2's outgoing packet?

209.165.200.227 Signup and view all the answers

What must be identified as step 4 when configuring dynamic NAT translations?

Which interfaces are inside. Signup and view all the answers

In translating the packet from PC1 to a global address, what does R2 replace?

The source address of the local network. Signup and view all the answers

Study Notes

NAT Configuration Commands

Define NAT pool named NAT-POOL2 with IP range 209.165.200.226 to 209.165.200.240 and subnet mask 255.255.255.224.
Create an access list (ACL 1) to permit the range 192.168.0.0/16 for NAT translation.
Configure NAT to translate inside local addresses from the specified access list using NAT-POOL2 with overload.
Specify the interface serial0/1/0 as inside NAT.
Specify the same interface as outside NAT for external traffic.

Packet Analysis in PAT

PC1 and PC2 send packets to servers Svr1 and Svr2.
First packet from PC1 is processed by R2, changing its source IP to the inside global address 209.165.200.225 before forwarding.
PC2's packet reaches R2 next; PAT modifies its source IP to 209.165.200.225.
Since PC2 shares the same source port as PC1, PAT increments the port number to ensure uniqueness, e.g., 1445.

Types of NAT

Static NAT

Establishes a one-to-one mapping of local and global addresses maintained by the network administrator.
Useful for servers needing a permanent address accessible from the internet.
Requires sufficient public IP addresses to accommodate all simultaneous sessions.

Dynamic NAT

Utilizes a pool of public IP addresses assigned on a first-come, first-served basis.
When an internal device requests external access, an available IP from the pool is assigned.
Like Static NAT, it requires enough public addresses for simultaneous sessions.

Port Address Translation (PAT)

Also known as NAT overload, allowing multiple private IPs to map to a single public IP.
Relies on unique source port numbers for each session, enabling differentiation of sessions within the same translated public IP.

Dynamic NAT Configuration Steps

Identify interfaces designated as inside and outside for NAT functionality.
Example commands include defining a NAT pool, creating an access list, and specifying NAT settings for interfaces.

Dynamic NAT Translation Process

Upon packet reception from PC1 and PC2 requesting server connections, R2 checks the ACL to determine if translation is needed.
First packet from PC1 is identified, and R2 assigns an available global IP from its pool, translating the inside source IP (e.g., 192.168.10.10) to a global address like 209.165.200.226.
The same translation occurs for the next PC, with each packet being routed with its new global address.

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Description

Test your knowledge on configuring NAT using Cisco commands. This quiz covers the essential steps and configurations needed to successfully set up NAT pools and access lists. Prepare to challenge your understanding of IP NAT principles and practical applications in networking.