Cisco CCNA (200-301)Network FundamentalsHard
A network administrator needs to provide internet access to a small branch office using a single public IPv4 address. Multiple internal devices in the office require access to external resources. Which networking technology will allow these multiple internal devices to share a single public IP address?
- ADynamic NAT
- BVPN
- CStatic NAT
- DPort Address Translation (PAT)
Show answer & explanationAnswer & explanation
Correct answer: D. Port Address Translation (PAT)
Port Address Translation (PAT), also known as NAT Overload, allows multiple internal private IP addresses to share a single public IPv4 address by using different source port numbers for each outbound connection. This is the most common method for small offices to access the internet with a limited number of public IPs.
Why the other options are wrong
- A. Dynamic NAT maps a pool of private IP addresses to a pool of public IP addresses, requiring multiple public IPs, not just a single one.
- B. VPNs (Virtual Private Networks) are used for secure, encrypted communication between networks or a client and a network, not primarily for sharing a single public IP for general internet access.
- C. Static NAT maps a single private IP address to a single public IP address, which doesn't allow multiple internal devices to share one public IP.
Port Address Translation (PAT)
Port Address Translation (PAT), also known as NAT Overload, is a form of Network Address Translation (NAT) that allows multiple devices on a private network to share a single public IPv4 address by using different source port numbers for each connection.
- Many-to-one translation of private to public IP addresses.
- Uses source port numbers to differentiate traffic from internal hosts.
- Commonly used for internet access in homes and small offices.
- Conserves public IPv4 addresses.
Memory trick: NAT is like a translator. Static is 1-to-1. Dynamic is 1-to-many. PAT is many-to-1 with ports.