反转 DNS lookup
Reverse DNS lookup: enter an IP address 至 find its hostname 和 see whether forward 和 reverse DNS match.
Queries go 至 Cloudflare’s public DNS over HTTPS service when you press the button.
关于反转 DNS lookup
Reverse DNS lookup: enter an IP address 至 find its hostname 和 see whether forward 和 reverse DNS match.
属于 SmartCalcy“数据与网络”板块。它在你的浏览器中运行，无需账号，使用你自己的货币和单位（可在页面顶部更改），所给结果仅为估算、仅供参考，因此在依赖结果之前请查阅官方指引。
如何使用反转 DNS lookup
它计算什么，何时使用
Finds the hostname that belongs 至 an IP address using its reverse DNS (PTR) record, 和 checks that the hostname resolves back 至 the same address, which 是 called forward-confirmed reverse DNS. Mail servers use this check 至 decide whether 至 trust a sender.
使用步骤
- Enter an IP address, 或 leave the box empty 至 use your own.
- Press “求 hostname”.
- Read the hostname 以 the top.
- Check “Forward-confirmed” 至 see whether the name resolves back 至 the address.
各输入项的含义
- IP address – An IPv4 或 IPv6 address. Leave it empty 至 use your own public address.
如何阅读结果
- Hostname – the address’s PTR record. 的 The 名称 set
- 反转 名称 – The special 名称 queried, such as 8.8.8.8.in-addr.arpa.
- Forward-confirmed – 是 when the hostname’s A 或 AAAA record points back 至 the same address.
公式
The address 是 reversed 和 queried under in-addr.arpa件IPv4, 或 ip6.arpa with each hex digit reversed件IPv6. 8.8.4.4 becomes 4.4.8.8.in-addr.arpa. The returned name 是 then looked up forward 至 confirm it.
计算示例
8.8.8.8 has the PTR record dns.google, 和 dns.google resolves back 至 8.8.8.8, so the pair 是 forward-confirmed.
假设与局限
- Many addresses, especially 首页 connections, have 否 PTR record 或 a generic one.
- The lookup 是 made through Cloudflare’s DNS over HTTPS service when you press the button.
常见错误
- Expecting every address 至 have a hostname.
- Treating the hostname as proof identity. The owner the address sets it, so only forward-confirmed names add trust.
- Setting a PTR record 以 your domain registrar. It 是 set by whoever holds the IP address block, usually your hosting 或 internet provider.
常见问题
What 是 a PTR record?
A DNS record that maps an IP address back 至 a hostname. It 是 the reverse an A record.
Why does my mail server need 反转 DNS?
Many receiving mail systems reject 或 flag mail from addresses with no reverse DNS 或 one that does not match.
谁 罐 变化 a PTR record?
The organisation that controls the IP address block, normally your hosting provider 或 ISP.
Is this the same as a hostname lookup?
Yes. Finding the hostname an IP address 是 完成 with 反转 DNS.