Inside Source NAT and PAT Configuration and Verification

46 questions

Question 21Question

A network administrator is configuring Port Address Translation (PAT) on a Cisco IOS router to map internal host traffic matched by access list 1515 to the IPv4 address assigned to public WAN interface GigabitEthernet0/0/1\text{GigabitEthernet0/0/1}. The inside and outside interfaces have already been designated using `ip nat inside` and `ip nat outside`, and `access-list 15 permit 172.16.10.0 0.0.0.255` is active. What exact Cisco IOS global configuration command must be entered to complete this Port Address Translation configuration?

Show answer & explanation

Answer: ip nat inside source list 15 interface GigabitEthernet0/0/1 overload; ip nat inside source list 15 interface gigabitethernet0/0/1 overload; ip nat inside source list 15 interface Gi0/0/1 overload; ip nat inside source list 15 interface gi0/0/1 overload

Answer

ip nat inside source list 15 interface GigabitEthernet0/0/1 overload
The command `ip nat inside source list 15 interface GigabitEthernet0/0/1 overload` accurately references the designated access list (15), binds it to the specified egress WAN interface (GigabitEthernet0/0/1), and enables Port Address Translation using the `overload` keyword.

Step-by-Step Solution

1
Identify the required NAT component structure
The command requires specifying inside source translation, matching traffic via access list 15, and linking to interface GigabitEthernet0/0/1.
Cisco IOS requires declaring the translation direction and source criteria.
2
Append the key Port Address Translation parameter
Add the keyword `overload` at the end of the command.
Without the `overload` keyword, Cisco IOS defaults to dynamic one-to-one NAT rather than Port Address Translation (many-to-one mapping using transport layer port numbers).

Key Concept

Inside Source PAT Configuration with Interface Overload
Estimated Time:1m 30s
Question 22Question

A network administrator configures Port Address Translation (PAT) on a Cisco IOS router so that internal hosts on the 10.10.50.0/2410.10.50.0/24 network can access external services through WAN interface GigabitEthernet0/0/1. The access list and global translation rules are configured as follows:

text
access-list 105 permit ip 10.10.50.0 0.0.0.255 any
ip nat inside source list 105 interface GigabitEthernet0/0/1 overload

During testing, internal clients cannot access external websites, and running `show ip nat translations` produces no output. An inspection of the interface configuration reveals:

text
interface GigabitEthernet0/0/0
description LAN Gateway
ip address 10.10.50.1 255.255.255.0
!
interface GigabitEthernet0/0/1
description WAN Interface
ip address 203.0.113.2 255.255.255.252
ip nat outside

Which configuration step on the router is required to enable successful address translation for the internal clients?

Show answer & explanation

Answer: Apply the command `ip nat inside` under interface GigabitEthernet0/0/0.

Answer

Apply the command `ip nat inside` under interface GigabitEthernet0/0/0.
For Cisco IOS NAT/PAT to process packets, interfaces connecting to internal networks must be explicitly configured with the `ip nat inside` command, and external-facing interfaces must be configured with `ip nat outside`. Because GigabitEthernet0/0/0 lacked `ip nat inside`, traffic entering from the LAN was routed normally without undergoing NAT evaluation.

Step-by-Step Solution

1
Identify NAT domain boundaries on the router interfaces.
GigabitEthernet0/0/1 is configured with `ip nat outside`, but GigabitEthernet0/0/0 lacks the `ip nat inside` designation.
Cisco IOS Network Address Translation requires at least one inside interface and one outside interface to trigger packet translation upon traversing the NAT boundary.
2
Evaluate the global NAT statement and access list configuration.
The global command `ip nat inside source list 105 interface GigabitEthernet0/0/1 overload` correctly references ACL 105 and specifies interface overload (PAT).
The syntax of the global NAT translation rule and referenced ACL is accurate.
3
Determine the necessary interface configuration fix.
Enter interface configuration mode for GigabitEthernet0/0/0 and execute `ip nat inside`.
Designating GigabitEthernet0/0/0 as the inside NAT interface allows the router to recognize incoming LAN traffic subject to NAT.

Key Concept

Inside and Outside NAT Interface Boundaries
Question 23Question

A network administrator is configuring Network Address Translation (NAT) on a Cisco IOS router interface connected to the internal local area network (GigabitEthernet0/0). What exact Cisco IOS interface configuration command designates this interface as the internal side for NAT translation?

Show answer & explanation

Answer: ip nat inside

Answer

ip nat inside
The command 'ip nat inside' is used in interface configuration mode on a Cisco IOS router to identify the interface connected to the private inside network. This designation is mandatory for the router to properly identify inbound traffic needing source translation.

Step-by-Step Solution

1
Identify the requirement for designating the LAN-facing interface in Cisco IOS NAT configuration.
Recognize that NAT requires defining which interfaces are on the inside (internal LAN) and which are on the outside (WAN/Internet).
Cisco IOS NAT needs explicit interface direction tagging to determine where packets arrive from and where they are headed.
2
Determine the exact interface configuration mode command.
The command is 'ip nat inside'.
This command tags the specified interface as part of the internal network boundary.

Key Concept

Designating inside interface for Cisco IOS NAT/PAT configuration
Question 24Question

A network administrator needs to configure a one-to-one static Network Address Translation (NAT) mapping on a Cisco IOS router. The internal host with private IPv4 address 10.1.1.5010.1.1.50 must be statically translated to the public IPv4 address 198.51.100.50198.51.100.50. What exact Cisco IOS global configuration command should be entered to establish this static NAT mapping?

Show answer & explanation

Answer: ip nat inside source static 10.1.1.50 198.51.100.50; ip nat inside source static 10.1.1.50 198.51.100.50

Answer

ip nat inside source static 10.1.1.50 198.51.100.50
The correct command syntax for establishing static NAT in Cisco IOS global configuration mode is `ip nat inside source static <inside-local-ip> <inside-global-ip>`. Substituting 10.1.1.5010.1.1.50 as the inside local IP and 198.51.100.50198.51.100.50 as the inside global IP yields `ip nat inside source static 10.1.1.50 198.51.100.50`.

Step-by-Step Solution

1
Identify the static NAT command structure in Cisco IOS.
The static NAT syntax is `ip nat inside source static <local-ip> <global-ip>`.
Static NAT maps a specific inside local address to a specific inside global address.
2
Substitute the specified inside local IP address (10.1.1.5010.1.1.50) and inside global IP address (198.51.100.50198.51.100.50) into the command structure.
The complete command becomes `ip nat inside source static 10.1.1.50 198.51.100.50`.
This establishes a permanent one-to-one translation between the private IP address and public IP address.

Key Concept

Static Inside Source Network Address Translation (NAT) Configuration
Question 25Question

A network administrator needs to configure Port Address Translation (PAT) on a Cisco IOS router so that multiple internal hosts defined in Access Control List 1 can share the IP address assigned to the WAN interface GigabitEthernet0/0/1. Which command correctly completes this configuration?

Show answer & explanation

Answer: ip nat inside source list 1 interface GigabitEthernet0/0/1 overload

Answer

The command 'ip nat inside source list 1 interface GigabitEthernet0/0/1 overload' correctly enables Port Address Translation (PAT) using the router's exit interface IP address.
The correct choice utilizes the 'ip nat inside source list 1 interface GigabitEthernet0/0/1 overload' command. This properly specifies that internal traffic matching access list 1 should be translated to the public IP assigned to interface GigabitEthernet0/0/1, while the 'overload' keyword enables Port Address Translation (PAT) so multiple hosts can share that single address via port multiplexing.

Step-by-Step Solution

1
Identify the requirement for interface-based PAT (Port Address Translation).
Dynamic translation for multiple hosts using a single interface IP requires referencing the inside source list, the outside interface name, and the 'overload' keyword.
The 'overload' keyword instructs the router to track unique source port numbers so multiple internal IP addresses can share one public IP address.
2
Evaluate the syntax structure of Cisco IOS NAT commands.
The correct global configuration command syntax is 'ip nat inside source list <acl-number> interface <interface-id> overload'.
This binds the matching ACL to the specified interface and enables port multiplexing.

Key Concept

Port Address Translation (PAT) Interface Overload Configuration
Question 26Question

A network administrator configures dynamic NAT on a Cisco IOS router using an IP pool named `INTERNET_POOL` (198.51.100.1198.51.100.1 to 198.51.100.2198.51.100.2) for hosts in the 10.20.30.0/2310.20.30.0/23 internal network. During testing, users observe that after two internal hosts establish outbound connections, no other internal hosts can access external sites. The output of `show ip nat statistics` shows total translations equal to 22 (00 static, 22 dynamic, 00 extended).

Configuration snippet:
text
ip nat pool INTERNET_POOL 198.51.100.1 198.51.100.2 netmask 255.255.255.252
access-list 15 permit 10.20.30.0 0.0.1.255
ip nat inside source list 15 pool INTERNET_POOL

Which TWO statements correctly identify the root cause of this issue and the solution required to allow all internal hosts to translate concurrently? (Select two.)

Select all that apply

Show answer & explanation

Answer: The current `ip nat inside source` command configures dynamic 1-to-1 NAT, which exhausts the pool after assigning both available public IP addresses.; Appending the `overload` keyword to the `ip nat inside source` command enables Port Address Translation (PAT), allowing multiple internal hosts to share pool IP addresses using unique Layer 4 port numbers.

Answer

The current `ip nat inside source` command configures dynamic 1-to-1 NAT, which exhausts the pool after assigning both available public IP addresses. Appending the `overload` keyword to the `ip nat inside source` command enables Port Address Translation (PAT), allowing multiple internal hosts to share pool IP addresses using unique Layer 4 port numbers.
Dynamic NAT without the `overload` keyword maps inside local IP addresses to inside global IP addresses on a strict 1-to-1 basis. Because `INTERNET_POOL` contains only two public IP addresses (198.51.100.1198.51.100.1 and 198.51.100.2198.51.100.2), only two hosts can translate simultaneously. To permit all hosts on the subnet to share these addresses concurrently, the `overload` keyword must be added to the end of the `ip nat inside source list 15 pool INTERNET_POOL` command to enable Port Address Translation (PAT).

Step-by-Step Solution

1
Analyze the existing router configuration and command output.
The command `ip nat inside source list 15 pool INTERNET_POOL` binds ACL 15 to the pool `INTERNET_POOL` without the `overload` keyword at the end.
Omitting `overload` specifies standard dynamic NAT (1-to-1 mapping) rather than PAT (many-to-1 or many-to-few mapping).
2
Evaluate the capacity of the NAT pool.
The pool `INTERNET_POOL` contains 2 IP addresses (198.51.100.1198.51.100.1 and 198.51.100.2198.51.100.2).
In 1-to-1 dynamic NAT, once 2 hosts initiate traffic, both pool addresses are checked out. The 3rd host cannot translate and its packets are dropped.
3
Determine the required CLI modification to support concurrent access for the entire 10.20.30.0/2310.20.30.0/23 network.
Modify the command to `ip nat inside source list 15 pool INTERNET_POOL overload`.
The `overload` keyword instructs Cisco IOS to track Layer 4 source port numbers (creating extended translations shown in `show ip nat translations`), allowing thousands of concurrent sessions across the public pool IP addresses.

Key Concept

Port Address Translation (PAT) Overload Keyword Requirement
Question 27Question

An administrator examines the following output from a Cisco router after configuring Network Address Translation to map private addresses to a defined address pool:

text
Router# show ip nat statistics
Total active translations: 1 (0 static, 1 dynamic; 0 extended)
Outside interfaces:
GigabitEthernet0/1
Inside interfaces:
GigabitEthernet0/0
Hits: 14 Misses: 0
Dynamic mappings:
-- Inside Source
[id 1] access-list 10 pool NAT_POOL refcount 1

Users on the internal subnet report that only one device at a time can successfully communicate with external networks. Which configuration change will resolve this issue and allow multiple concurrent internal hosts to share the translation pool?

Show answer & explanation

Answer: Append the overload keyword to the ip nat inside source list 10 pool NAT_POOL command.

Answer

Append the overload keyword to the ip nat inside source list command to enable Port Address Translation.
The show ip nat statistics output reveals '0 extended translations', meaning the router is performing 1-to-1 dynamic NAT rather than Port Address Translation (PAT). Adding the overload keyword to the 'ip nat inside source list 10 pool NAT_POOL' statement enables port multiplexing, which permits multiple inside hosts to share pool addresses simultaneously.

Step-by-Step Solution

1
Analyze the output of show ip nat statistics.
The statistics show 0 extended translations and 1 dynamic translation, indicating standard dynamic NAT (1-to-1 mapping) rather than PAT.
Without extended translations, each internal host consumes an entire IP address from the pool, preventing other hosts from translating once pool addresses are checked out.
2
Identify the missing keyword in the NAT configuration.
The current dynamic mapping uses 'access-list 10 pool NAT_POOL' without 'overload'.
The 'overload' keyword instructs Cisco IOS to track transport layer port numbers, enabling multiple hosts to share single public IP addresses.
3
Select the correct command modification.
Reconfigure using 'ip nat inside source list 10 pool NAT_POOL overload'.
This enables PAT on the pool and allows concurrent outbound access for all hosts matching ACL 10.

Key Concept

Port Address Translation (PAT) / Inside Source NAT Overload Configuration
Question 28Question

A network administrator is configuring Port Address Translation (PAT) on a Cisco router so that internal hosts on the 10.1.1.0/2410.1.1.0/24 subnet can access the Internet using the public IP address assigned to the WAN interface GigabitEthernet0/0/1GigabitEthernet0/0/1. Access List 11 has already been configured to permit traffic from 10.1.1.0/2410.1.1.0/24. Which two actions are required to complete this PAT configuration? (Select two.)

Select all that apply

Show answer & explanation

Answer: Configure the command `ip nat inside source list 1 interface GigabitEthernet0/0/1 overload` in global configuration mode.; Apply the command `ip nat inside` under the interface connected to the internal LAN.

Answer

To complete PAT using an exit interface IP address, the administrator must designate the LAN interface with `ip nat inside` and configure the global translation statement `ip nat inside source list 1 interface GigabitEthernet0/0/1 overload`.
Port Address Translation (PAT) using an exit interface requires defining the internal interface with `ip nat inside` and executing `ip nat inside source list <acl> interface <interface> overload` globally. The `overload` keyword ensures multiple internal hosts can share the single public IP address by assigning unique source ports to each session.

Step-by-Step Solution

1
Identify the internal boundary interface and assign the NAT role.
Apply `ip nat inside` on the LAN interface connected to internal hosts.
Cisco IOS requires identifying inside and outside interfaces so it knows which packets trigger NAT processing.
2
Configure the global PAT source translation statement with interface overload.
Enter `ip nat inside source list 1 interface GigabitEthernet0/0/1 overload` in global configuration mode.
The `overload` keyword enables Port Address Translation (PAT), allowing multiple internal private IP addresses to share a single public IP address using distinct TCP/UDP port numbers.

Key Concept

Inside Source Port Address Translation (PAT) Interface Overload Configuration
Estimated Time:1m 0s
Question 29Question

A network administrator is implementing Port Address Translation (PAT) using an IP address pool on a Cisco IOS router. Internal devices belong to the 172.16.0.0/12172.16.0.0/12 private network range. Standard IP access list 1515 has already been created to identify inside traffic with the command `access-list 15 permit 172.16.0.0 0.15.255.255`. The public IP addresses assigned by the ISP for translation are 203.0.113.10203.0.113.10 through 203.0.113.14203.0.113.14 with subnet mask 255.255.255.248255.255.255.248. Which TWO configuration commands must be executed on the router to correctly instantiate the pool and map the inside ACL traffic to allow multiple internal hosts to share these public IP addresses simultaneously?

Select all that apply

Show answer & explanation

Answer: ip nat pool OUTSIDE_POOL 203.0.113.10 203.0.113.14 netmask 255.255.255.248; ip nat inside source list 15 pool OUTSIDE_POOL overload

Answer

The correct commands are 'ip nat pool OUTSIDE_POOL 203.0.113.10 203.0.113.14 netmask 255.255.255.248' and 'ip nat inside source list 15 pool OUTSIDE_POOL overload'.
Configuring multi-host Port Address Translation (PAT) across an IP pool requires two key elements: first, defining the pool of available public IP addresses with its range and netmask ('ip nat pool OUTSIDE_POOL 203.0.113.10 203.0.113.14 netmask 255.255.255.248'), and second, referencing that pool in the inside source translation directive with the 'overload' keyword ('ip nat inside source list 15 pool OUTSIDE_POOL overload').

Step-by-Step Solution

1
Define the public NAT IP address pool
Configured 'ip nat pool OUTSIDE_POOL 203.0.113.10 203.0.113.14 netmask 255.255.255.248'
Establishes the range of publicly routable IPv4 addresses provided by the ISP available for translation.
2
Map the access list traffic to the pool using Port Address Translation
Executed 'ip nat inside source list 15 pool OUTSIDE_POOL overload'
Binds the traffic identified in ACL 15 to the public pool and uses the 'overload' keyword to track unique layer 4 port numbers, enabling many private IP addresses to share the pool addresses.

Key Concept

Inside Source Dynamic PAT Configuration with Address Pool
Question 30Question

A network engineer is configuring Port Address Translation (PAT) on a Cisco IOS router using a dynamic NAT pool named PUBLICPOOLPUBLIC_POOL (203.0.113.10203.0.113.10 to 203.0.113.12203.0.113.12). Internal endpoints reside on the 172.16.10.0/24172.16.10.0/24 network, which is matched by standard Access Control List 15. Which two configuration actions must be performed on the router to correctly enable PAT for internal hosts and designate interface directionality? (Select two.)

Select all that apply

Show answer & explanation

Answer: Apply the command ip nat inside source list 15 pool PUBLIC_POOL overload in global configuration mode.; Configure the command ip nat inside under the LAN-facing interface (e.g., GigabitEthernet0/0).

Answer

To configure PAT using an IP pool, the global command must include the 'overload' keyword ('ip nat inside source list 15 pool PUBLIC_POOL overload') to permit port multiplexing, and the internal interface must be designated with 'ip nat inside'.
Enabling PAT with a defined pool requires the 'overload' keyword at the end of the 'ip nat inside source list <acl> pool <name> overload' command structure. Additionally, Cisco IOS routers require explicit interface domain definitions, where 'ip nat inside' is applied to LAN interfaces connected to internal devices.

Step-by-Step Solution

1
Identify the requirement for PAT overload with an IP pool.
Dynamic NAT pool mapping requires appending 'overload' to enable port address translation multiplexing.
Without 'overload', Cisco IOS performs dynamic 1-to-1 NAT, limiting active translations to the number of IPs in the pool.
2
Identify required interface NAT role assignments.
The LAN interface facing internal hosts must be marked with 'ip nat inside'.
Cisco IOS requires explicit NAT domain boundaries ('inside' and 'outside') to trigger translation on packet traversal.
3
Validate RFC 1918 IP address matching in ACL statements.
The subnet 172.16.10.0/24172.16.10.0/24 is private, whereas 172.32.10.0/24172.32.10.0/24 is public address space.
Matching public addresses in internal NAT ACLs fails to translate actual private endpoint traffic.

Key Concept

Inside Source Port Address Translation (PAT) Pool Configuration and Interface Assignment
Question 31Question

An administrator needs to configure Port Address Translation (PAT) on a Cisco IOS router to allow multiple internal hosts matched by Access Control List 15 to share the single IPv4 address assigned to interface GigabitEthernet0/1 for internet access. Which command correctly enables this configuration?

Show answer & explanation

Answer: ip nat inside source list 15 interface GigabitEthernet0/1 overload

Answer

The command 'ip nat inside source list 15 interface GigabitEthernet0/1 overload' correctly configures Port Address Translation (PAT).
The command stating 'ip nat inside source list 15 interface GigabitEthernet0/1 overload' is correct because it properly binds inside source traffic allowed by ACL 15 to the interface's IP address and appends the 'overload' keyword, enabling PAT (Port Address Translation) via TCP/UDP port mapping.

Step-by-Step Solution

1
Identify the requirement for translating multiple private IP addresses to a single interface IP address.
Port Address Translation (PAT) using the overload keyword on an interface is required.
The overload keyword allows multiple internal IP addresses to map to a single public IP address using distinct layer 4 source port numbers.
2
Construct the Cisco IOS configuration syntax for interface-based PAT.
The correct command syntax is 'ip nat inside source list <acl> interface <type/number> overload'.
This binds the inside source traffic matched by the specified ACL to the outbound interface IP address with port overloading.

Key Concept

Port Address Translation (PAT) Configuration using Interface Overload
Question 32Question

A network engineer is configuring Port Address Translation (PAT) using an IP address pool on a Cisco IOS router. An access list named ACL_LAN (ACL 10) matches internal traffic, and an IP address pool named GIG_POOL has been defined for global addresses. What exact global configuration command completes this PAT configuration by linking access list 10 to GIG_POOL with port overload capability?

Show answer & explanation

Answer: ip nat inside source list 10 pool GIG_POOL overload; ip nat inside source list 10 pool GIG_POOL overload

Answer

ip nat inside source list 10 pool GIG_POOL overload
The command 'ip nat inside source list 10 pool GIG_POOL overload' explicitly binds internal traffic defined by ACL 10 to the public address pool GIG_POOL while enabling port overloading (PAT).

Step-by-Step Solution

1
Identify the standard access list matching inside traffic.
Access list 10 matches internal subnets.
NAT source list parameter requires referencing the defined access list number or name.
2
Identify the target public IP address pool name.
The NAT pool name is specified as GIG_POOL.
The pool keyword requires the exact name of the previously configured IP address pool.
3
Append the port address translation overload keyword.
Adding overload allows multiple inside local addresses to share public IP addresses in the pool using layer 4 port numbers.
Omitting overload configures dynamic one-to-one NAT without port multiplexing, causing address exhaustion when pool IP addresses are fully allocated.

Key Concept

Inside source Port Address Translation (PAT) using an IP address pool requires the overload keyword appended to the 'ip nat inside source list <acl> pool <pool-name>' command.
Question 33Question

A network administrator is configuring Port Address Translation (PAT) on a Cisco IOS router to allow internal users access to the Internet using a single public IP address assigned to the GigabitEthernet0/1 interface. The administrator has already configured the Access Control List (ACL) and the inside/outside interfaces. What exact Cisco IOS keyword must be appended to the end of the 'ip nat inside source list 1 interface GigabitEthernet0/1' command to enable port-level address translation?

Show answer & explanation

Answer: overload; the overload keyword; overload keyword

Answer

overload
The 'overload' keyword instructs the Cisco IOS router to perform Port Address Translation (PAT), enabling multiple private IPv4 addresses to share a single public IP address by tracking source port numbers.

Step-by-Step Solution

1
Identify the requirement for Port Address Translation (PAT) using an interface IP address.
PAT enables multiple private IP addresses to share a single public IP address by mapping distinct layer 4 port numbers.
Without the overload capability, static NAT or standard dynamic NAT requires a 1-to-1 IP mapping.
2
Determine the necessary Cisco IOS command syntax.
The command syntax is 'ip nat inside source list <acl> interface <interface> overload'.
The 'overload' keyword specifically enables PAT, allowing port tracking for dynamic address translation.

Key Concept

Port Address Translation (PAT) Interface Overload Syntax
Question 34Question

An enterprise router is configured for dynamic Network Address Translation (NAT) using an IP pool containing four public IP addresses (198.51.100.1198.51.100.1 to 198.51.100.4198.51.100.4). Internal users report that only four devices can access external resources at any given time, and subsequent connection attempts by other hosts fail until an existing session terminates. Which configuration change will allow all internal hosts to share the public IP address pool simultaneously?

Show answer & explanation

Answer: Append the overload keyword to the ip nat inside source list pool command.

Answer

Append the overload keyword to the ip nat inside source list pool command.
The correct response specifies appending the overload keyword to the dynamic NAT configuration statement (e.g., ip nat inside source list 1 pool NAT_POOL overload). This enables Port Address Translation (PAT), allowing multiple internal devices to share the public addresses by tracking unique source port numbers.

Step-by-Step Solution

1
Analyze the reported issue
Dynamic NAT without PAT provides strict 1-to-1 translations, restricting concurrent internet access to the exact number of public IP addresses in the pool (4 hosts).
Omitting port-level translation causes the router to exhaust available public addresses after 4 active sessions.
2
Identify the required Cisco IOS command enhancement
Appending the 'overload' keyword converts dynamic NAT to Port Address Translation (PAT).
PAT tracks source TCP/UDP port numbers, enabling thousands of inside private hosts to multiplex over the same pool of public IP addresses.

Key Concept

Port Address Translation (PAT) Overload Configuration
Estimated Time:1m 15s
Question 35Question

An administrator notices that while the first host on the internal network (10.1.10.0/2410.1.10.0/24) can access the internet, subsequent hosts are unable to establish outbound connections simultaneously. Inspecting Router1 reveals the following running configuration:

text
access-list 105 permit ip 10.1.10.0 0.0.0.255 any
ip nat pool EDGE_POOL 203.0.113.5 203.0.113.5 prefix-length 32
ip nat inside source list 105 pool EDGE_POOL

Command output from `show ip nat statistics` confirms:
text
Total active translations: 1 (0 static, 1 dynamic, 0 extended)
Outside interfaces: GigabitEthernet0/1
Inside interfaces: GigabitEthernet0/0
Hits: 142 Misses: 18
Dynamic mappings:
-- Inside Source
access-list 105 pool EDGE_POOL ref count 1

Which configuration modification must be applied to Router1 to allow all internal hosts on the 10.1.10.0/2410.1.10.0/24 network to share the single IP address assigned to `EDGE_POOL` concurrently?

Show answer & explanation

Answer: Append the overload keyword to the statement: ip nat inside source list 105 pool EDGE_POOL overload

Answer

Appending the overload keyword to the inside source NAT configuration command (ip nat inside source list 105 pool EDGE_POOL overload) enables Port Address Translation (PAT).
The configuration present on Router1 establishes standard dynamic 1-to-1 NAT. Because the pool contains only one IP address (203.0.113.5), only the first internal host receives a translation. Appending the overload keyword modifies the translation engine to perform Port Address Translation (PAT), allowing multiple inside local hosts to share a single inside global address by using unique transport-layer port numbers.

Step-by-Step Solution

1
Analyze the configuration and verification output
The command 'ip nat inside source list 105 pool EDGE_POOL' without the overload keyword configures standard dynamic NAT. Because EDGE_POOL contains only a single IP address (203.0.113.5), only 1 dynamic translation entry (extended = 0) can exist at any given time.
Standard dynamic NAT allocates global IP addresses on a one-to-one basis. Once all pool addresses are exhausted, additional hosts attempting connection are dropped (misses increase).
2
Identify the missing component for port multiplexing
To allow multiple internal hosts to share one global IP address, Layer 4 port numbers must be tracked using Port Address Translation (PAT).
PAT requires the 'overload' keyword at the end of the 'ip nat inside source' command.
3
Formulate the correct configuration command
Execute 'ip nat inside source list 105 pool EDGE_POOL overload' on Router1.
This enables extended translations, allowing thousands of concurrent internal sockets to multiplex over port numbers assigned to 203.0.113.5.

Key Concept

Port Address Translation (PAT) Overload Keyword Requirement
Estimated Time:2m 0s
Question 36Question

A network administrator is implementing Port Address Translation (PAT) on a Cisco IOS router to allow hosts on the internal subnet 10.45.10.0/2410.45.10.0/24 to access the Internet. The WAN interface GigabitEthernet0/0/1 receives its dynamic IP address from the ISP, while interface GigabitEthernet0/0/0 connects to the internal LAN. Which two configuration steps or commands are required to successfully enable PAT using the WAN interface address? (Select TWO options.)

Select all that apply

Show answer & explanation

Answer: Specify the translation mapping using the command ip nat inside source list 1 interface GigabitEthernet0/0/1 overload; Identify NAT roles on the router interfaces by configuring ip nat inside on GigabitEthernet0/0/0 and ip nat outside on GigabitEthernet0/0/1

Answer

Port Address Translation (PAT) using a router interface requires defining the internal and external NAT interface designations (ip nat inside / ip nat outside) and creating the NAT statement referencing the matching ACL and interface with the overload keyword (ip nat inside source list 1 interface GigabitEthernet0/0/1 overload).
To successfully establish Port Address Translation (PAT) using an interface address, two mandatory requirements must be fulfilled: defining the NAT boundary interface roles (ip nat inside on the LAN side and ip nat outside on the WAN side) and writing the translation command linking the matching ACL to the WAN interface with the overload keyword present.

Step-by-Step Solution

1
Designate the internal and external NAT interfaces.
GigabitEthernet0/0/0 is configured with ip nat inside and GigabitEthernet0/0/1 is configured with ip nat outside.
Cisco IOS NAT needs to identify ingress and egress traffic boundaries to know when to apply translation rules.
2
Define an access list matching the internal subnet traffic.
Standard ACL permits 10.45.10.0 0.0.0.255.
The ACL acts as the interesting traffic filter to identify packets eligible for translation.
3
Configure the inside source PAT statement using the interface and overload keywords.
Command ip nat inside source list 1 interface GigabitEthernet0/0/1 overload is applied.
The overload keyword instructs Cisco IOS to track layer 4 TCP/UDP port numbers, enabling thousands of internal hosts to share one public IP address.

Key Concept

Inside Source PAT Configuration
Estimated Time:2m 0s
Question 37Question

A network administrator is configuring Port Address Translation (PAT) on a Cisco IOS router to allow internal hosts in the 172.16.50.0/24172.16.50.0/24 subnet to access the Internet using the public IP address on interface GigabitEthernet0/0/0. Internal users report that they cannot establish any outbound internet connections. The running configuration reveals the following details:

interface GigabitEthernet0/0/0
ip address 203.0.113.1 255.255.255.248
ip nat outside
!
interface GigabitEthernet0/0/1
ip address 172.16.50.1 255.255.255.0
!
ip access-list standard NAT_ACL
permit 172.16.50.0 0.0.0.255
!
ip nat inside source list NAT_ACL interface GigabitEthernet0/0/0 overload

Which configuration change must be made on the router to resolve this issue?

Show answer & explanation

Answer: Configure the ip nat inside command under interface GigabitEthernet0/0/1.

Answer

Configure the ip nat inside command under interface GigabitEthernet0/0/1.
For Cisco IOS NAT to operate, at least one interface must be designated as 'ip nat inside' and at least one interface as 'ip nat outside'. In the provided configuration, interface GigabitEthernet0/0/1 lacks the 'ip nat inside' command, so packets arriving from internal hosts are not identified for translation.

Step-by-Step Solution

1
Analyze the existing router configuration for NAT/PAT components.
Interface GigabitEthernet0/0/0 is properly marked with 'ip nat outside', NAT_ACL permits 172.16.50.0/24172.16.50.0/24, and the global translation statement maps NAT_ACL to GigabitEthernet0/0/0 with 'overload'.
For Cisco IOS NAT/PAT to process packets, interfaces must be designated as inside or outside, and traffic must cross between them.
2
Inspect the internal interface configuration.
Interface GigabitEthernet0/0/1 is missing the 'ip nat inside' command.
Without 'ip nat inside' on the internal gateway interface, incoming packets from 172.16.50.0/24172.16.50.0/24 are routed normally without undergoing Network Address Translation.
3
Identify the required fix.
Add 'ip nat inside' under interface GigabitEthernet0/0/1 configuration.
This establishes the boundary between internal private addresses and the external public interface, enabling PAT processing.

Key Concept

Inside and Outside NAT Interface Designation
Estimated Time:1m 30s
Question 38Question

A network engineer is tasking a Cisco IOS router with Port Address Translation (PAT) to enable Internet access for internal endpoints on the 192.168.20.0/24192.168.20.0/24 network using the public IPv4 address assigned to interface GigabitEthernet0/0/1. Which two configuration steps are required on the router to accomplish this requirement? (Select two.)

Select all that apply

Show answer & explanation

Answer: Define an IPv4 Access Control List (ACL) that permits traffic originating from the internal 192.168.20.0/24192.168.20.0/24 subnet.; Execute the global configuration command `ip nat inside source list <ACL> interface GigabitEthernet0/0/1 overload`.

Answer

To configure interface-based PAT (overload) on Cisco IOS, an administrator must define an ACL identifying the inside local host network and bind that ACL to the outside WAN interface using `ip nat inside source list <ACL> interface <interface-id> overload`.
Configuring interface-based Port Address Translation (PAT) requires creating an ACL that permits internal host addresses (192.168.20.0/24192.168.20.0/24) and linking that ACL to the egress interface with `ip nat inside source list <ACL> interface GigabitEthernet0/0/1 overload`. The `overload` keyword is mandatory to enable layer 4 port tracking so multiple hosts can share one IP.

Step-by-Step Solution

1
Identify the internal host network requiring translation.
Internal subnet is identified as 192.168.20.0/24192.168.20.0/24.
An Access Control List (ACL) must be configured to match traffic coming from 192.168.20.0/24192.168.20.0/24.
2
Bind the matching ACL to the external interface using PAT.
The command `ip nat inside source list <ACL> interface GigabitEthernet0/0/1 overload` is configured.
The `overload` keyword allows multiple internal hosts to share the single interface IP address by tracking unique L4 port numbers.

Key Concept

Port Address Translation (PAT) interface overload configuration
Question 39Question

An administrator needs to verify active Port Address Translation (PAT) sessions on a Cisco IOS router to inspect how inside local IP addresses and source port numbers are mapped to inside global addresses and translated port numbers. What exact Cisco IOS command displays the active NAT translation table?

Show answer & explanation

Answer: show ip nat translations; sh ip nat translations; show ip nat translation; sh ip nat trans

Answer

show ip nat translations
The command 'show ip nat translations' displays all current active Network Address Translation and Port Address Translation mappings in the router's state table, showing exact protocol and port translations.

Step-by-Step Solution

1
Identify the operational requirement for inspecting active PAT session mappings on a Cisco IOS router.
The objective requires displaying live translation bindings, including transport-layer protocol ports.
Active translation sessions are maintained dynamically in the router's active NAT translation table.
2
Specify the Cisco IOS privileged EXEC verification command that displays the translation table.
Executing 'show ip nat translations' prints the active list of translated addresses and port combinations.
This command outputs inside local, inside global, outside local, and outside global socket mappings.

Key Concept

Inside Source NAT and PAT Verification
Estimated Time:1m 0s
Question 40Question

A network engineer is configuring Port Address Translation (PAT) on a Cisco IOS router to allow hosts on the internal private subnet 10.10.5.0/2410.10.5.0/24 to access the Internet using the router's WAN interface GigabitEthernet0/1GigabitEthernet0/1. An Access Control List (ACL 10) has already been created to permit traffic from 10.10.5.0/2410.10.5.0/24. Which two configuration steps are required on the router to complete this setup?

Select all that apply

Show answer & explanation

Answer: Apply the command ip nat inside on the local LAN interface and ip nat outside on interface GigabitEthernet0/1.; Issue the global configuration command ip nat inside source list 10 interface GigabitEthernet0/1 overload.

Answer

The required steps are designating the LAN interface as inside and WAN interface as outside, and issuing the global command ip nat inside source list 10 interface GigabitEthernet0/1 overload.
To successfully establish Port Address Translation (PAT) using a router's exit interface, interfaces must be marked correctly as inside/outside boundaries, and the global NAT translation rule must reference the matching ACL along with the outside interface name and the essential 'overload' parameter.

Step-by-Step Solution

1
Identify and configure NAT interface roles
The internal interface facing 10.10.5.0/24 is designated with 'ip nat inside', and the WAN interface GigabitEthernet0/1 is designated with 'ip nat outside'.
Cisco IOS requires traffic boundaries to be designated so it knows where translation must take place.
2
Configure the global PAT translation rule
Execute 'ip nat inside source list 10 interface GigabitEthernet0/1 overload'.
The 'overload' keyword instructs the router to translate multiple private source IP addresses onto the single IP assigned to GigabitEthernet0/1 by tracking unique source port numbers.

Key Concept

Port Address Translation (PAT) Interface Designation and Overload Syntax
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