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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 NAT pool named `INTERNET_POOL` for internal endpoints matched by access list `10`. Which global configuration command correctly enables PAT using this address pool?

  1. ip nat inside source list 10 pool INTERNET_POOL overloadAnswer
  2. B
    ip nat inside source list 10 pool INTERNET_POOL
  3. C
    ip nat inside source list 10 pool 172.16.10.1 172.16.10.10 overload
  4. D
    ip nat outside source list 10 pool INTERNET_POOL overload

Answer

The command 'ip nat inside source list 10 pool INTERNET_POOL overload' correctly enables Port Address Translation using the specified pool.
The correct command uses 'ip nat inside source list 10 pool INTERNET_POOL overload'. The 'inside source' parameter specifies translation for outbound traffic originating inside the network, 'list 10' identifies hosts permitted by ACL 10, 'pool INTERNET_POOL' designates the global address pool, and 'overload' enables port-level multiplexing (PAT) so multiple internal endpoints can share pool addresses simultaneously.

Step-by-Step Solution

1
Identify the direction of translation.
Internal hosts initiating outbound connections require 'inside source' translation.
Inside source NAT translates private local IP addresses to public global addresses.
2
Identify the method of matching source addresses and defining the public addresses.
Access list 10 filters inside local hosts, and the named pool 'INTERNET_POOL' defines the public IPv4 addresses.
The 'list 10 pool INTERNET_POOL' syntax binds the ACL host match condition to the pool range.
3
Determine the keyword required for Port Address Translation (PAT).
Adding the 'overload' keyword enables multiplexing multiple internal hosts onto pool addresses using unique TCP/UDP port numbers.
Without 'overload', Cisco IOS restricts dynamic NAT to a strict 1-to-1 IP address mapping.

Key Concept

Port Address Translation (PAT) configuration using dynamic address pools in Cisco IOS
Estimated Time:1m 0s
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Topics

Inside Source NAT and PAT Configuration and Verification

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