When you type a URL and press Enter, which of the following best describes the initial step the browser takes to resolve the domain?

When you type a URL and press Enter, which of the following best describes the initial step the browser takes to resolve the domain?

• A. It checks caches in the browser, the operating system, the router, and the ISP for the DNS record.
• B. It immediately opens a TCP connection to the server's IP.
• C. It queries the DNS server via ARP on the local network.
• D. It prompts the user to manually enter an IP address.

Answer: (A)

The initial step is to look for a DNS mapping in caches. The browser first checks its own DNS cache for a recently resolved domain-to-IP entry. If it’s there, the IP is used right away, and the page starts loading quickly. If not, the OS often keeps its own DNS cache, and the local network device such as the router may cache DNS responses as well. The ISP’s DNS servers also cache lookups. This multi-layer caching lets most requests be answered without contacting external servers, which speeds things up and reduces network traffic. If the mapping isn’t found in any cache, the system then queries the configured DNS servers to resolve the domain, after which the browser can connect to the obtained IP. ARP is used to map IP addresses to MAC addresses on the local network and isn’t involved in translating domain names. You wouldn’t normally be asked to manually enter an IP address—the standard flow is to resolve the domain automatically via DNS.

The initial step is to look for a DNS mapping in caches. The browser first checks its own DNS cache for a recently resolved domain-to-IP entry. If it’s there, the IP is used right away, and the page starts loading quickly. If not, the OS often keeps its own DNS cache, and the local network device such as the router may cache DNS responses as well. The ISP’s DNS servers also cache lookups. This multi-layer caching lets most requests be answered without contacting external servers, which speeds things up and reduces network traffic. If the mapping isn’t found in any cache, the system then queries the configured DNS servers to resolve the domain, after which the browser can connect to the obtained IP. ARP is used to map IP addresses to MAC addresses on the local network and isn’t involved in translating domain names. You wouldn’t normally be asked to manually enter an IP address—the standard flow is to resolve the domain automatically via DNS.