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