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Zorluk: ZorInside Source NAT and PAT Configuration and Verification

A network engineer on router R1 configures dynamic Network Address Translation using an IP pool containing two public addresses (203.0.113.1203.0.113.1 to 203.0.113.2203.0.113.2) to service the internal subnet 172.16.10.0/24172.16.10.0/24. Access Control List 10 permits traffic from 172.16.10.0/24172.16.10.0/24. The router configuration includes the statement `ip nat inside source list 10 pool NAT_POOL`. During peak operating hours, users report that after two simultaneous connections are established, all additional internal hosts fail to reach external destinations. Output from `show ip nat statistics` displays active translations at maximum pool capacity with zero port translation entries. Which configuration change will allow all internal hosts to share the public addresses concurrently?

  1. Append the `overload` keyword to the `ip nat inside source list 10 pool NAT_POOL` command.Cevap
  2. B
    Modify Access Control List 10 to permit source traffic from 172.32.10.0/24172.32.10.0/24 to match public routing tables.
  3. C
    Add a standard Access Control List statement with `permit any` at the beginning of ACL 10 to bypass pool tracking.
  4. D
    Reassign the `ip nat inside` directive to the WAN interface and `ip nat outside` to the LAN interface.

Cevap

Append the `overload` keyword to the `ip nat inside source list 10 pool NAT_POOL` command to enable Port Address Translation (PAT).
The command `ip nat inside source list 10 pool NAT_POOL` without the `overload` keyword performs dynamic 1-to-1 NAT mapping. With only two IP addresses in the pool, only the first two internal hosts receive translations; all subsequent translation attempts fail once the pool is exhausted. Appending the `overload` keyword activates Port Address Translation (PAT), allowing thousands of connections from internal hosts to share the pool IP addresses by tracking unique L4 transport port numbers.

Adım Adım Çözüm

1
Analyze the existing NAT configuration and symptoms.
The statement `ip nat inside source list 10 pool NAT_POOL` configures standard dynamic 1-to-1 NAT. Since the pool contains only two public IP addresses (203.0.113.1203.0.113.1 and 203.0.113.2203.0.113.2), only two internal hosts can obtain translations concurrently.
Without port multiplexing, each host requires an entire public IP address, leading to pool exhaustion when a third host attempts to transmit.
2
Identify the required Cisco IOS keyword to allow port multiplexing.
The `overload` keyword enables PAT, mapping multiple private IP addresses to the same public IP address using distinct source port numbers.
Adding `overload` allows hundreds of simultaneous internal sessions to share the two pool IP addresses.

Anahtar Kavram

Port Address Translation (PAT) vs. Dynamic 1-to-1 NAT
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