Addresses on a Network: IP Addresses, Hostnames and Paths
IP addresses identify destinations for network data. Ordinary devices on one local network need distinct addresses, while separate private networks can reuse them. A web address contains a hostname and a path. DNS can look up IP addresses for the hostname.
What a learner can do afterwards
- Explain local address conflicts, address changes and reuse on separate private networks
- Separate a hostname and path in a web address and identify the network part of a stated /24 IPv4 example
- Describe hostname-to-IP lookup, saved lookup results and what failed lookup prevents
1 · Read
Networks use destination IP addresses to deliver data. In ordinary local-network use, duplicate addresses can cause a conflict. An address can change; it is not a permanent identity for one computer. Separate private networks can reuse addresses. A device can have several addresses, and a router can let several devices share a public address.
An IPv4 address is written as four numbers from 0 to 255, separated by dots. In 192.168.6.25/24, the /24 prefix means the first three numbers form the network part: 192.168.6. The last number, 25, is the device part within that network. Other prefix lengths place the boundary elsewhere. The dots alone do not specify it.
In https://museum.example/maps/hall, https is the scheme, museum.example is the hostname, and /maps/hall is the path. The hostname identifies the service being requested. It can lead to several server addresses. The path identifies a resource at that service, such as a page. This made-up address is for reading, not visiting.
DNS, the Domain Name System, can look up IP addresses for a hostname. It does not translate the path or fetch the page. A browser can reuse a usable saved lookup result instead of making a fresh query.
Hostname resolution means looking up IP addresses for a hostname. "Could not be resolved" means that lookup failed. Without a usable saved address, the browser cannot contact the service by that hostname. DNS queries may already have been sent. Successful lookup does not guarantee a page will load: the server or connection can still fail. Typing an IP address instead of a hostname does not always load the same website.
IP addresses guide delivery. A hostname identifies a service; a path identifies a resource. DNS can find addresses for the hostname, and saved results can be reused.
Two readings and six flashcards about address scope, prefixes and web names were written for this dataset.
More to read
The scope of an address
A destination IP address helps a network deliver data. Two ordinary devices using the same address on one local network can cause a conflict.
That rule does not make an address a permanent identity worldwide. An address can change, and a device can have more than one. Separate private networks can reuse private addresses. Two unrelated homes can each have a device at 192.168.1.40 without those matching local addresses conflicting between the homes.
Several devices can also share a public address through a router that tracks their connections.
A prefix, a hostname and a path
Dots separate the four numbers in an IPv4 address. A prefix specifies the network boundary. For 192.168.7.23/24, the network part is 192.168.7 and the device part is 23. Other prefixes can place the boundary within a dotted number.
A web address has different parts. In https://library.example/books, library.example is the hostname and /books is the path. DNS can look up IP addresses for the hostname. It does not fetch the path's resource.
A hostname can lead to several servers, and one server can serve several hostnames. A usable saved lookup result can avoid a fresh query. Failed page loading alone does not identify a DNS problem.
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