nslookup

有些时候, user 可能会想要手动查询 DNS 上一些数据, 或者是要看看 DNS 是否有问题, 此时我们最常用的工具就是 nslookup 了, 基本上 nslookup 会根据 /etc/resolv.conf 的内容去找到所要使用的 local DNS server.

使用说明

打入 nslookup 命令后, 会看到 > 提示符号, 此时打 ? 就会出现 nslookup 说明
Default Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

>?

$Id: nslookup.help,v 8.4 1996/10/25 18:09:41 vixie Exp $

Commands: (identifiers are shown in uppercase, [] means optional)
NAME - print info about the host/domain NAME using default server
NAME1 NAME2 - as above, but use NAME2 as server
help or ? - print info on common commands; see nslookup(1) for details
set OPTION - set an option
all - print options, current server and host
[no]debug - print debugging information
[no]d2 - print exhaustive debugging information
[no]defname - append domain name to each query
[no]recurse - ask for recursive answer to query
[no]vc - always use a virtual circuit
domain=NAME - set default domain name to NAME
srchlist=N1[/N2/.../N6] - set domain to N1 and search list to N1,N2, etc.
root=NAME - set root server to NAME
retry=X - set number of retries to X
timeout=X - set initial time-out interval to X seconds
querytype=X - set query type, e.g., A,ANY,CNAME,HINFO,MX,PX,NS,PTR,SOA,TXT,WKS,SRV,NAPTR
port=X - set port number to send query on
type=X - synonym for querytype
class=X - set query class to one of IN (Internet), CHAOS, HESIOD or ANY
server NAME - set default server to NAME, using current default server
lserver NAME - set default server to NAME, using initial server
finger [USER] - finger the optional USER at the current default host
root - set current default server to the root
ls [opt] DOMAIN [> FILE] - list addresses in DOMAIN (optional: output to FILE)
-a - list canonical names and aliases
-h - list HINFO (CPU type and operating system)
-s - list well-known services
-d - list all records
-t TYPE - list records of the given type (e.g., A,CNAME,MX, etc.)
view FILE - sort an 'ls' output file and view it with more
exit - exit the program, ^D also exits
>^D

Interactive/Noninteractive (交谈式/非交谈式)

执行 nslookup 时可以直接在后面跟着我们要查询的资料, 那么 nslookup 会直接把结果传回来
如果只打入 nslookup [enter], 则进入交谈模式, 出现提示符号 >, 此时 nslookup 会等待 user input command.

tung@traveler:~> nslookup www.yohoo.com
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

Non-authoritative answer:
Name: yohoo.com
Address: 216.116.98.143
Aliases: www.yohoo.com

tung@traveler:~> nslookup
Default Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

> www.yohoo.com
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

Non-authoritative answer:
Name: yohoo.com
Address: 216.116.98.143
Aliases: www.yohoo.com

Authoritative/Non-Authoritative

在查询时有时会出现 Non-authoritative answer, 代表这个答案是由 local DNS 的 cache 中直接读出来的, 而不是 local DNS 向真正负责这个 domain 的 name server 问来的.

常用的一些 option/command

1. set all
可以得知目前 nslookup 的一些 default 设定值
tung@traveler:~> nslookup
Default Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

> set all
Default Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

Set options:
nodebug defname search recurse
nod2 novc noignoretc port=53
querytype=A class=IN timeout=5 retry=4
root=a.root-servers.net.
domain=ee.ncku.edu.tw
srchlist=ee.ncku.edu.tw

2. server dns_server_ip
表示将内定的 local DNS 换成另一部 server
Ex: server 140.116.2.6

3. set type=any
表示在查询某个 domain name 时, 将和这个 domain name 的一些相关数据一并显示出来
> set type=any
> www.yohoo.com
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

Non-authoritative answer:
www.yohoo.com canonical name = yohoo.com

Authoritative answers can be found from:
yohoo.com nameserver = ns1.netgateway.net
yohoo.com nameserver = ns2.netgateway.net
ns1.netgateway.net internet address = 216.116.98.7
ns2.netgateway.net internet address = 216.116.98.8

在上面的这个例子, 我们除了知道 www.yohoo.com 的 IP 外, 我们还得知了 yohoo.com 是由哪部 name server 在负责的. 因此如果想要知道 www.yohoo.com 真正在 yohoo.com 上的记录是如何, 而不要有 local DNS cache 中传回的资料, 我们可以配合使用 server 这个 command 将 default local DNS 改为负责 yohoo.com 的 DNS, 然后再查询一次
> server 216.116.98.7
Default Server: ns1.netgateway.net
Address: 216.116.98.7

> www.yohoo.com
Server: ns1.netgateway.net
Address: 216.116.98.7

Name: yohoo.com
Address: 216.116.98.143
Aliases: www.yohoo.com

4. set type=ptr
本来要由 IP 反查 domain name时, 在直接打 IP 就行了, 但如果已经下了 type=any 的话, 要由 IP 反查时就没那么方便了, 此时 IP 4 个数字要倒着写, 最后还要加上 in-addr.arpa. 以查 140.116.72.219 为例, 要输入的就是 219.72.116.140.in-addr.arpa
tung@traveler:~> nslookup
Default Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

> 140.116.72.219
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

Name: garfield.ee.ncku.edu.tw
Address: 140.116.72.219

> set type=any
> 140.116.72.219
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

*** sun4.ee.ncku.edu.tw can't find 140.116.72.219: Non-existent host/domain
> 219.72.116.140.in-addr.arpa
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

219.72.116.140.in-addr.arpa name = garfield.ee.ncku.edu.tw
72.116.140.IN-ADDR.ARPA nameserver = sun4.ee.ncku.edu.tw
sun4.ee.ncku.edu.tw internet address = 140.116.72.14

另外一个办法就是先下 set type=ptr 或 set type=a 命令, 脱离 type=any 模式, 再进行 IP 反查 domain name 的 command
> set typr=ptr
> 140.116.72.219
Server: sun4.ee.ncku.edu.tw
Address: 140.116.72.14

219.72.116.140.in-addr.arpa name = garfield.ee.ncku.edu.tw
72.116.140.IN-ADDR.ARPA nameserver = sun4.ee.ncku.edu.tw
sun4.ee.ncku.edu.tw internet address = 140.116.72.14

5. ls domain
这个命令是要求 name server 将其负责的 zone 内容 show 出来, 这个动作相当于 name server 的整份记录从 server 端传回给 nslookup 这个程序, 这种传回整个 zone 的动作叫作 zone transfer
> set type=any
> ee.ncku.edu.tw
Server: cs.ncku.edu.tw
Address: 140.116.2.6

ee.ncku.edu.tw nameserver = sun4.ee.ncku.edu.tw
ee.ncku.edu.tw preference = 1, mail exchanger = eembox.ee.ncku.edu.tw
ee.ncku.edu.tw internet address = 140.116.72.15
ee.ncku.edu.tw
origin = sun4.ee.ncku.edu.tw
mail addr = root.sun4.ee.ncku.edu.tw
serial = 1999033001
refresh = 3600 (1H)
retry = 900 (15M)
expire = 3600000 (5w6d16h)
minimum ttl = 3600 (1H)
ee.ncku.edu.tw nameserver = sun4.ee.ncku.edu.tw
sun4.ee.ncku.edu.tw internet address = 140.116.72.14
eembox.ee.ncku.edu.tw internet address = 140.116.72.15
> ls ee.ncku.edu.tw
Default Server: cs.ncku.edu.tw
Address: 140.116.2.6

> [sun4.ee.ncku.edu.tw]
$ORIGIN ee.ncku.edu.tw.
@ 1H IN A 140.116.72.15
hdlib4 1H IN A 140.116.72.4
ds114 1H IN A 140.116.72.114
hdlib5 1H IN A 140.116.72.5
ds115 1H IN A 140.116.72.115
yokoyama1 1H IN A 140.116.227.217
hdlib6 1H IN A 140.116.72.6
ds116 1H IN A 140.116.72.116
yokoyama2 1H IN A 140.116.227.218
ds117 1H IN A 140.116.72.117
ds120 1H IN A 140.116.72.120
ds118 1H IN A 140.116.72.118
ds121 1H IN A 140.116.72.121
ds119 1H IN A 140.116.72.119
ds122 1H IN A 140.116.72.122
ds123 1H IN A 140.116.72.123
intelab01 1H IN A 140.116.227.39