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nslookup

query Internet name servers interactively

References

  • man nslookup

Synopsis

nslookup [-option] [name | -] [server]

Options

  • See man nslookup

Usage

A (default)

$ nslookup weibo.com
Server:         10.13.8.25
Address:        10.13.8.25#53

Non-authoritative answer:
Name:   weibo.com
Address: 123.125.104.197
Name:   weibo.com
Address: 123.125.104.26

MX

$ nslookup -type=mx weibo.com
Server:         10.13.8.25
Address:        10.13.8.25#53

Non-authoritative answer:
weibo.com       mail exchanger = 10 mx.sina.net.

Authoritative answers can be found from:
weibo.com       nameserver = ns3.sina.com.
weibo.com       nameserver = ns1.sina.com.cn.
weibo.com       nameserver = ns2.sina.com.cn.
weibo.com       nameserver = ns4.sina.com.
weibo.com       nameserver = ns3.sina.com.cn.
weibo.com       nameserver = ns4.sina.com.cn.
mx.sina.net     internet address = 202.108.37.31
ns1.sina.com.cn internet address = 202.106.184.166
ns2.sina.com.cn internet address = 61.172.201.254
ns3.sina.com    internet address = 61.172.201.254
ns3.sina.com.cn internet address = 123.125.29.99
ns4.sina.com    internet address = 123.125.29.99
ns4.sina.com.cn internet address = 121.14.1.22

CNAME

$ nslookup -type=cname weibo.com
Server:         10.13.8.25
Address:        10.13.8.25#53

Non-authoritative answer:
*** Can't find weibo.com: No answer

Authoritative answers can be found from:
weibo.com
        origin = ns1.sina.com.cn
        mail addr = zhihao.staff.sina.com.cn
        serial = 1
        refresh = 28800
        retry = 7200
        expire = 604800
        minimum = 600

Interactive

$ nslookup
> baidu.com
Server:         10.13.8.25
Address:        10.13.8.25#53

Non-authoritative answer:
Name:   baidu.com
Address: 123.125.115.110
Name:   baidu.com
Address: 220.181.57.216
> sspai.com
Server:         10.13.8.25
Address:        10.13.8.25#53

Non-authoritative answer:
Name:   sspai.com
Address: 119.23.141.248
>

Records

References

Record Description
CNAME 别名，用于将多个域名绑定到同一个IP地址上
A 将域名或者子域名转换为一个32位的IP地址，也可以存储其他有价值的信息
MX 将域名绑定到邮件服务器上

A

Address record

  • The record A specifies IP address (IPv4) for given host.
  • A records are used for conversion of domain names to corresponding IP addresses.

AAAA

IPv6 address record

  • The record AAAA (also quad-A record) specifies IPv6 address for given host.
  • So it works the same way as the A record and the difference is the type of IP address.

CNAME

Canonical Name record

  • The CNAME record specifies a domain name that has to be queried in order to resolve the original DNS query.
  • Therefore CNAME records are used for creating aliases of domain names.
  • CNAME records are truly useful when we want to alias our domain to an external domain.
  • In other cases we can remove CNAME records and replace them with A records and even decrease performance overhead.
  • 个人经验：用于设置子域名

MX

Mail exchanger record

  • Maps a domain name to a list of message transfer agents for that domain
    • The MX resource record specifies a mail exchange server for a DNS domain name.
    • The information is used by Simple Mail Transfer Protocol (SMTP) to route emails to proper hosts.
    • Typically, there are more than one mail exchange server for a DNS domain and each of them have set priority.

NS

Name server record

  • Delegates a DNS zone to use the given authoritative name servers
    • A DNS zone is any distinct, contiguous portion of the domain name space in the Domain Name System (DNS) for which administrative responsibility has been delegated to a single manager.
    • An authoritative name server is a name server that gives answers in response to questions asked about names in a DNS zone.

TXT

Text record

  • Originally for arbitrary human-readable text in a DNS record.
  • Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework, DKIM, DMARC, DNS-SD, etc.

SRV

Service locator

  • Generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX.
    • An SRV (Service) record points one domain to another domain name using a specific destination port.
    • SRV records allow specific services, such as VOIP or IM, to be be directed to a separate location.