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Difficulty: MediumInside Source NAT and PAT Configuration and Verification

A network engineer is configuring Port Address Translation (PAT) on a Cisco IOS router using an IP address pool. Access Control List 10 matches internal private IPv4 addresses, and the NAT pool is named `OUTSIDE_POOL`. To allow multiple internal hosts to share the addresses in `OUTSIDE_POOL` by multiplexing Layer 4 port numbers, which single keyword must be appended to the end of the `ip nat inside source list 10 pool OUTSIDE_POOL` command?

Answer: overload / the overload keyword

Answer

overload
Appending the keyword `overload` to the `ip nat inside source list <acl> pool <pool_name>` command enables Port Address Translation (PAT). This allows Cisco IOS to translate both IP addresses and transport layer port numbers, enabling many internal private IP addresses to share public IP addresses in the pool.

Step-by-Step Solution

1
Identify the requirement for Port Address Translation (PAT) using an IP address pool.
Standard dynamic NAT assigns public IP addresses to private IP addresses on a one-to-one basis.
Without port tracking, dynamic pool NAT runs out of available public IPv4 addresses when internal hosts exceed the pool size.
2
Determine the necessary Cisco IOS command modifier to enable port multiplexing.
Appending the keyword `overload` instructs the router to track transport-layer port numbers (PAT).
The `overload` keyword enables multiple internal sockets to share pool addresses simultaneously.

Key Concept

Inside Source Port Address Translation (PAT) Pool-based Configuration
Estimated Time:1m 0s
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Topics

Inside Source NAT and PAT Configuration and Verification

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