IPv4, the full name of Internet Protocol version 4, is the earliest widely used protocol version in the history of the Internet. A standard IPv4 address consists of four groups of numbers ranging from 0 to 255, separated by periods, for example: 192.168.0.1. There are about 4.3 billion addresses in this address format worldwide, which seems a lot, but with the explosive growth of Internet users and devices, it has actually been in short supply. Although IPv6 has been available for many years, IPv4 still dominates a large number of infrastructures.

　　The DNS server (Domain Name System Server) is responsible for converting domain names like "xxx.com" into specific IP addresses. This process is called domain name resolution. Imagine if you need to remember a string of digital addresses every time you visit a website, the Internet would not be as popular as it is today. DNS establishes a mapping between website names and IP addresses. Users only need to remember the domain name, and DNS will automatically find the corresponding IP address in the background. It can be said that there is no DNS.

　　Now let's take a look at how these two work together in the actual network architecture. Suppose you enter "xxxx.com" in the browser, the system will first query whether there is an IP address corresponding to this domain name in the local cache, and it will initiate a request to the locally configured DNS server. This server may know the target IP address, or it may not know it, so it will continue to query the root DNS server, the top-level domain DNS server, and the authoritative DNS server step by step, and finally find the correct IPv4 address and return it to you, and then you can successfully access the website.

　　The relationship between IPv4 address and DNS is like the linkage between phone book and phone number. IPv4 is the terminal of communication, and DNS is the indexing mechanism in the middle. The operating efficiency between the two directly affects the web page loading speed, network stability, and even the overall Internet experience of users.

　　Enterprises and webmasters also attach great importance to the quality of DNS servers. A slow-responding DNS will cause web page loading delays, and even frequent resolution failures during peak hours. In order to optimize network access, most websites will choose to deploy multiple DNS servers, and even use CDN (content distribution network) for DNS load balancing. High-quality DNS also has network security functions such as preventing DNS hijacking and cache poisoning, which are equally important for website operators.

　　Although IPv4 address resources are scarce, there are still a large number of secondary markets for IPv4 address leasing and selling transactions, especially some site groups, IDC industries, and cloud service providers are extremely dependent on such resources. Some large enterprises have thousands of independent IPv4 addresses, just to achieve independent deployment between different domain names, IP distribution strategies or SEO optimization. Although this method is being carefully evaluated, its existence in the market shows that IPv4 is still a core resource that cannot be completely replaced today.

　　For ordinary users, setting up a reliable DNS server is also an important step to improve the network experience. For example, many families or companies will use addresses provided by public DNS service providers, such as Google DNS (8.8.8.8 and 8.8.4.4), Cloudflare DNS (1.1.1.1), OpenDNS, etc. The DNS nodes of these service providers are widely distributed, with fast resolution speed and high stability, and also provide some security protection functions. Users only need to modify the DNS settings in the operating system or router to get a significant improvement in the Internet experience.

　　From the perspective of SEO, the speed and stability of DNS resolution also affect the availability score of the website. Search engines monitor a website's access response speed, whether it is stable and reachable, whether there are DNS errors, and other issues. Once the DNS response is slow or the resolution fails frequently, the search engine may lower the website's ranking. This is definitely a detail that cannot be ignored for websites doing Google SEO. Many professional SEO teams will choose to use a stable, low-latency DNS server when deploying the server, or even use a self-built DNS system to ensure maximum controllability.

　　There is also a deeper technical point - reverse DNS resolution (PTR record). This mechanism uses the IP address to look up the domain name, which is very critical in some mail servers, firewalls, and identity recognition systems. An IP address without reverse DNS settings can easily be identified as a spam source when sending emails, and thus be blocked. Many high-quality VPS providers provide PTR record customization functions to help users avoid this problem. For webmasters, every setting of the DNS system may directly affect whether the website can be accessed and whether it can be trusted by search engines.

　　We cannot ignore the importance of DNS cache. When a DNS server resolves an IP address, it usually saves it temporarily in the cache, so that the next time the same domain name is queried, there is no need to repeat the search. This greatly improves the resolution efficiency. However, a long cache time may also cause the domain name to still point to the old address after the change, causing access failure. Reasonable setting of TTL value (Time To Live) has become a detail that must be controlled in DNS operation.

　　Back to IPv4, in terms of network allocation, IP resources in different regions are allocated and managed by different RIRs (Regional Internet Registries). APNIC in Asia, ARIN in North America, RIPE NCC in Europe, etc. are responsible for managing IPv4 resources in their regions. Because IPv4 is exhausted, major institutions also encourage users to switch to IPv6, but due to factors such as compatibility and device support, the global popularity of IPv6 is still slowly advancing. Therefore, for many website operators and system architects, how to reasonably use existing IPv4 resources is still the focus of daily work.

　　IPv4 addresses and DNS servers play an indispensable role in the operation of the Internet. They are not just cold technical parameters, but also the core elements of building user Internet experience, website stability, security and search engine performance. For webmasters, what kind of DNS service to choose, how to manage their own IPv4 resources, and whether to reasonably set DNS resolution strategies are all important factors affecting the success or failure of a website. For ordinary users, configuring a stable and fast DNS may make daily Internet access faster and smoother.