Which statement correctly describes SNAT and DNAT?

• A. DNAT changes destination addresses; SNAT changes source addresses
• B. SNAT changes source addresses; DNAT changes destination addresses
• C. Both SNAT and DNAT change only port numbers
• D. SNAT and DNAT are the same thing

Answer: (B)

SNAT and DNAT are two ways a NAT device rewrites IP addresses to enable connections between networks. The key idea is that one type changes the source address as traffic leaves your network, while the other changes the destination address as traffic comes in. SNAT rewrites the source IP to the device’s public IP so outgoing packets appear to originate from that public address; when replies arrive, the NAT translates them back to the original internal host. DNAT, on the other hand, takes traffic addressed to a public IP and changes the destination to a specific internal host and port, which is how inbound connections (like a public web server) are directed inside your network. This distinction—source address being changed for outbound traffic, and destination address being changed for inbound traffic—captures the exact roles of SNAT and DNAT. The idea that they only modify ports isn’t accurate, and while some setups use port translation as well (PAT), the primary difference described here is which header field is rewritten.