IP Address

An IP address is the numeric identity a server answers on. DNS turns a human-friendly domain into this address, then the browser sends its request there. On a hosting account the address decides which machine receives your visitors.

Two formats

IPv4 is written as four decimal octets, for example 103.28.14.55. IPv6 uses eight hexadecimal groups, such as 2001:0db8:85a3::8a2e:0370:7334, offers a far larger pool, and is covered separately in IPv6. Most shared plans in Indonesia still show only IPv4, so treat IPv6 support as something to verify rather than assume.

What the address is used for

First, vhost resolution: on older servers the address selected which site to serve, while modern nginx and Apache separate sites by the Host header. Second, outbound mail, because receiving servers match the address against a PTR record through reverse DNS. Third, rate limiting, since firewalls and counters often key on the source address, which is how one shared address can trigger Error 429.

Shared versus dedicated

A shared IP serves tens or hundreds of accounts on one server and is the default on shared plans. A dedicated IP belongs to you alone, usually a paid add-on or standard on a VPS and dedicated server. HTTPS once demanded its own address because a certificate needed one name per address, but SSL/TLS with SNI now lets a single address serve many certificates, so that reason has mostly disappeared. Consider a dedicated IP if you send heavy mail and want your reputation separated from your neighbours, see Dedicated IP. For a blog, a company profile, or a small store, a shared address is more than enough.

The expensive misunderstanding

Upgrading to a dedicated IP feels like an instant deliverability fix. Without a matching PTR record the new address still looks anonymous to receiving servers, and reputation rests far more on SPF, DKIM, DMARC, and how you actually send, all unpacked in Email Deliverability. The reverse also holds: a shared IP can fall in reputation because one neighbour spammed, and every account on that address carries the cost. During a migration the server address almost always changes, because each provider uses its own block, so update A and AAAA records and wait for propagation before you blame the new host.

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