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Difficulty: Very hardInside Source NAT and PAT Configuration and Verification

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?

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
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Topics

Inside Source NAT and PAT Configuration and Verification

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