When the cname of a domain name fails to be resolved to a nonexistent domain name or the cname cannot be resolved, what error does the client prompt?

Today, the customer service Meimei asked me if the client nslookup a domain name prompts the following error:

650) this. width = 650; "src =" http://s3.51cto.com/wyfs02/M00/11/67/wKioL1LOXWfyw6btAAX_tBS0rYE611.bmp "title =" 111.bmp "alt =" wKioL1LOXWfyw6btAAX_tBS0rYE611.bmp "/>

Let's take a look at the correct parsing process:

650) this. width = 650; "src =" http://s3.51cto.com/wyfs02/M01/11/67/wKiom1LOXibDkRSeABAB2KHNoMg158.bmp "title =" 111.bmp "alt =" wkiom1loxibdkrseab2khnomg158.bmp "/>

I originally said that if the local DNS resolution of this domain name fails, it prompts that the domain name does not exist. If the domain name cname is not resolved, it should prompt that the resolution fails, later, I found a Domain Name and tried it myself. I understood it wrong. If the cname domain name cannot be resolved, it also prompts that the domain name does not exist.

For example, if I transfer te4.sportsvc.cn CNAME to www.fanfeildld.com, but www.fanfeildld.com cannot be parsed,

650) this. width = 650; "src =" http://s3.51cto.com/wyfs02/M00/11/67/wKioL1LOXqHDX1D7AAM4iJ63VOM149.bmp "title =" 111.bmp "alt =" wKioL1LOXqHDX1D7AAM4iJ63VOM149.bmp "/>

Take a look at the dig diagram:

650) this. width = 650; "src =" http://s3.51cto.com/wyfs02/M02/11/67/wKioL1LOXvLjPQjnAA3ByHJfRN4666.bmp "title =" 111.bmp "alt =" wKioL1LOXvLjPQjnAA3ByHJfRN4666.bmp "/>

We can see that cname is parsed. Because cname cannot be parsed, The nxdomain prompt is displayed.

Then look at the nslookup diagram:

650) this. width = 650; "src =" http://s3.51cto.com/wyfs02/M01/11/67/wKiom1LOXzeRrH9DAAAt3abHGso432.bmp "title =" 111.bmp "alt =" wKiom1LOXzeRrH9DAAAt3abHGso432.bmp "/>

The system also prompts that the domain name does not exist.

The result is as follows: we can enable the nslookup set d2 mode, and check the specific parsing process. We can also see that after the cname is parsed, no resolution is available.

> Set d2

> Te3.sportsvc.cn.

Cc-core.chinacache.local Server

Address: 192.168.1.199

------------

SendRequest (), len 33

HEADER:

Opcode = QUERY, id = 10, rcode = NOERROR

Header flags: query, want recursion

Questions = 1, answers = 0, authority records = 0, additional = 0

QUESTIONS:

Te3.sportsvc.cn, type = A, class = IN

------------

------------

Got answer (140 bytes ):

HEADER:

Opcode = QUERY, id = 10, rcode = NXDOMAIN

Header flags: response, want recursion, recursion avail.

Questions = 1, answers = 1, authority records = 1, additional = 0

QUESTIONS:

Te3.sportsvc.cn, type = A, class = IN

ANSWERS:

-> Te3.sportsvc.cn

Type = CNAME, class = IN, dlen = 22

Canonical name = www.fantefeildld.com

Ttl = 3515 (58 mins 35 secs)

Authority records:

-> Com

Type = SOA, class = IN, dlen = 61

Ttl = 815 (13 mins 35 secs)

Primary name server = a.gtld-servers.net

Responsible mail addr = nstld.verisign-grs.com

Serial = 1389254445

Refresh = 1800 (30 mins)

Retry = 900 (15 mins)

Expire = 604800 (7 days)

Default TTL = 86400 (1 day)

------------

This article from the "linux open source-continuous summary..." blog, please be sure to keep this source http://fantefei.blog.51cto.com/2229719/1350166