PTR 记录
Reverse DNS — maps an IP back to a hostname.
PTR 记录是什么？
PTR records live in the special in-addr.arpa (IPv4) and ip6.arpa (IPv6) zones. They are set by whoever owns the IP block (ISP, cloud provider) and translate an address back to a name. Mail servers and many security tools use reverse DNS for verification and logging.
区域文件示例
34.216.184.93.in-addr.arpa. 3600 IN PTR example.com.
常见用例
- ▸Pass outgoing-mail reputation checks — mail receivers require PTR forward-confirmed reverse DNS (FCrDNS).
- ▸Friendly logs — Apache, Nginx, syslog and SIEMs annotate IPs with hostnames.
- ▸Tracing in tracerouting — hop names are PTR records.
- ▸Allow-listing by hostname rather than IP in some security tools.
常见坑
You can almost never edit PTR yourself — you must ask your ISP / cloud provider (AWS Route 53 lets EC2 customers set PTR via support ticket; DigitalOcean and Hetzner expose it in the UI).