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Difficulty: EasyInside Source NAT and PAT Configuration and Verification

A network administrator is setting up Port Address Translation (PAT) on a Cisco IOS router using a public address pool named `PAT_POOL` and Access Control List `5`. Which two commands are required to correctly establish PAT and configure the LAN interface to participate in address translation? (Select two.)

  1. ip nat inside source list 5 pool PAT_POOL overloadAnswer
  2. ip nat insideAnswer
  3. C
    ip nat inside source list 5 pool PAT_POOL
  4. D
    ip nat outside source list 5 pool PAT_POOL overload

Answer

The two required commands are 'ip nat inside source list 5 pool PAT_POOL overload' entered in global configuration mode and 'ip nat inside' entered under the LAN interface configuration mode.
Configuring Port Address Translation (PAT) with an IP pool requires appending the 'overload' parameter to the global 'ip nat inside source list' command. Additionally, the internal interface connected to the local network must be identified with the interface-level command 'ip nat inside'.

Step-by-Step Solution

1
Identify the global configuration command for pool-based PAT
Determine that 'ip nat inside source list 5 pool PAT_POOL overload' is required to map inside local hosts matching ACL 5 to the PAT_POOL while enabling port overloading.
The 'overload' keyword allows multiple private internal IP addresses to share public IP addresses in the pool by tracking unique TCP/UDP port numbers.
2
Identify the interface configuration command for internal boundary identification
Select 'ip nat inside' on the LAN interface.
Cisco IOS routers require explicit designation of NAT boundaries to determine where packet translation takes place.

Key Concept

Inside Source Port Address Translation (PAT) configuration requiring the overload keyword and inside interface designation.
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Topics

Inside Source NAT and PAT Configuration and Verification

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