有客户要做邮件服务器，向机房申请IP反向解析，如何知道是否生效？最简单的办法：ping -a 173.212.248.98 如果能ping出一个域名，就说明反解析成功了！

反解析IP范例：

ping -a 173.212.248.98

Pinging www.ctohome.com  [173.212.248.98] with 32 bytes of data:

Reply from 173.212.248.98: bytes=32 time=258ms TTL=51
Reply from 173.212.248.98: bytes=32 time=257ms TTL=51
Reply from 173.212.248.98: bytes=32 time=257ms TTL=51
Reply from 173.212.248.98: bytes=32 time=257ms TTL=51

Ping statistics for 173.212.248.98:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 257ms, Maximum = 258ms, Average = 257ms

另一个方法nslookup查询IP反解析：

Doc环境下 ,输入 nslookup 回车 ,然后输入 ip 回车, 如果有name，那么就说明反解析成功

nslookup

> 173.212.248.98
Server:  ns.wuhan.net.cn
Address:  202.103.24.68

Name:   www.ctohome.com
Address:  173.212.248.98