DNS & DHCP

What it is

DHCP automatically assigns IP addresses (and other network configuration) to devices joining a network; DNS resolves human-readable domain names into the IP addresses actually needed to route traffic — two foundational, often-invisible protocols most networking depends on.

Key points

• DHCP lease process: a device requests an address, the DHCP server offers one from its available pool, and the device receives it for a lease duration — without DHCP, every device would need manual IP configuration, which doesn't scale.
• DNS resolution chain: a query typically walks from a local resolver up through root, TLD, and authoritative name servers — understanding this chain is what makes DNS propagation delays and misconfigurations debuggable.
• DNS caching and TTL: resolvers cache results for a time-to-live period set by the domain owner — a low TTL enables fast changes (e.g. during a migration) at the cost of more frequent lookups; a high TTL reduces load but slows how fast changes propagate.
• Both protocols are extremely high-leverage failure points — when "the whole application is down" turns out to be a DNS or DHCP issue, it usually explains why it looked like everything failed at once.