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Zorluk: OrtaInside Source NAT and PAT Configuration and Verification

A Cisco router connects an internal LAN on interface GigabitEthernet0/0 (172.16.50.0/24172.16.50.0/24) to an ISP link on interface GigabitEthernet0/1 (198.51.100.2/30198.51.100.2/30). The network engineer issues the global command `ip nat inside source list 15 interface GigabitEthernet0/1 overload` to enable Port Address Translation (PAT). However, internal hosts cannot reach the Internet and no translations appear in the NAT table. The running configuration reveals the following interface settings:

text
interface GigabitEthernet0/0
ip address 172.16.50.1 255.255.255.0
!
interface GigabitEthernet0/1
ip address 198.51.100.2 255.255.255.252
ip nat outside

Which configuration command must be applied to interface GigabitEthernet0/0 to enable address translation?

  1. Apply `ip nat inside` under interface GigabitEthernet0/0 configuration mode.Cevap
  2. B
    Remove the `overload` keyword from the global `ip nat inside source list 15 interface GigabitEthernet0/1 overload` statement.
  3. C
    Modify Access Control List 15 to match public range `172.32.50.0 0.0.0.255` instead of private range `172.16.50.0 0.0.0.255`.
  4. D
    Configure `ip helper-address 198.51.100.2` under interface GigabitEthernet0/0 to forward translation packets to the WAN interface.

Cevap

Apply `ip nat inside` under interface GigabitEthernet0/0 configuration mode.
For Cisco IOS NAT/PAT to function, the router must know which interface represents the internal network and which interface represents the external network. The output shows `ip nat outside` on GigabitEthernet0/1, but GigabitEthernet0/0 is missing `ip nat inside`. Without this designation, packets entering GigabitEthernet0/0 are routed normally without triggering NAT evaluation.

Adım Adım Çözüm

1
Analyze the given interface configuration for NAT boundary markers.
Interface GigabitEthernet0/1 is designated with `ip nat outside`, but GigabitEthernet0/0 lacks any NAT boundary designation.
Cisco IOS NAT routing logic requires packets to traverse from an interface designated as `ip nat inside` to one designated as `ip nat outside` (or vice versa) for translation rules to trigger.
2
Identify the required command to complete the NAT setup on the internal interface.
Configuring `ip nat inside` on GigabitEthernet0/0 establishes the internal NAT boundary.
This allows traffic originating from subnet 172.16.50.0/24172.16.50.0/24 entering GigabitEthernet0/0 to be evaluated by the `ip nat inside source list 15 interface GigabitEthernet0/1 overload` rule.

Anahtar Kavram

Inside and Outside NAT Interface Designation
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Konular

Inside Source NAT and PAT Configuration and Verification

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