Cisco CCNA (200-301)IP ServicesEasy
A network administrator needs to configure a Cisco router to always translate the internal IP address 192.168.1.10 to the public IP address 203.0.113.5 for all outbound traffic. Which of the following commands would accomplish this?
- Aip nat inside source static tcp 192.168.1.10 80 203.0.113.5 80
- Bip nat inside source static 192.168.1.10 203.0.113.5
- Cip nat pool STATIC_POOL 203.0.113.5 203.0.113.5 netmask 255.255.255.252
- Dip nat outside source static 192.168.1.10 203.0.113.5
Show answer & explanationAnswer & explanation
Correct answer: B. ip nat inside source static 192.168.1.10 203.0.113.5
This question tests the basic command for static NAT. The 'ip nat inside source static' command is used to map a single internal IP address to a single external IP address. Option B correctly uses this command for a one-to-one static translation.
Why the other options are wrong
- A. This command specifies TCP port translation, which is not required for a simple one-to-one static IP address mapping for all traffic.
- C. This command creates a NAT pool, which is typically used for dynamic NAT or PAT, not for a single static one-to-one mapping.
- D. The 'ip nat outside' command is used for translating destination addresses from the outside to the inside, or for source addresses originating from the outside, which is not the scenario here.
Static NAT
A one-to-one mapping of a private IP address to a public IP address, ensuring the same public IP is always used for a specific private host.
- Always uses the same public IP for a given private IP.
- Useful for publicly accessible servers on a private network.
- Configured using 'ip nat inside source static' command.
Memory trick: Static NAT is like a fixed postal address for your internal server – always the same public face.