Shulou(Shulou.com)06/01 Report--

According to cnnic's dns (2001:dc7:1000::1) packet grab analysis, because I think some of his addresses refuse to resolve are more referential.

I grabbed the packets of the four domain names www.baidu.com www.sina.com.cn www.google.com ipv6.tsinghua.edu.cn and got the following test results.

Test results:

1. In the process of parsing, ipv6 takes precedence over ipv4 parsing. This process is analyzed by grabbing the serial number of the package.

2. There is no way to resolve www.baidu.com through 2001:dc7:1000::1, but it can be resolved through the ip address of 192.168.0.223.

When accessing www.baidu.com, it is also accessed through the address resolved by ipv4 and the access is normal.

3. Www.sina.com.cn can be parsed through 2001:dc7:1000::1, and the resolved addresses are: 202.106.184.166 is Unicom address, 61.172.201.254 is telecom, 123.125.29.99 is Unicom, 121.14.1.22 is telecom.

At the same time, the company's ipv4 dns also parses the www.sina.com.cn. The resolved address is: 218.30.108.232

Through tracert, I found that although ipv6 is parsed first, it is not accessed through the address resolved by ipv6. For more information, please see the screenshot process.

4. Although www.google.com cannot be parsed through 2001:dc7:1000::1, it can be parsed to 216.58.208.36 and 2a00:1450:4001:817::2004 through ipv4 colleagues.

However, when you visit, you go out through ipv6. You can see the three-way handshake of tcp through ipv6 when you visit google through the screenshot below.

5. Because google has the resources of both ipv6 and ipv4, I tested it again when I replaced the dns of the Science and Technology Network. I don't see ipv6dns parsing in the grab bag, but what is parsed through nslookup is

Name: www.google.com

Addresses: 200:2:2e52:ae44::

93.46.8.89

The address resolved by Ipv4 is: non-authoritative reply:

Non-authoritative response:

Name: www.google.com.hk

Addresses: 200:2:4e10:310f::

78.16.49.15

At the time of the visit, the result is the same ipv6. Although several pc were found trying to access google with ipv4 in the grab package, ipv4 did not get a response.

Summary above: ipv6 takes precedence over ipv4 parsing when dns parsing, but ipv6 takes precedence when co-existing ipv4 and ipv6 resources.

When Ipv6 dns ipv4dns resolves the corresponding ipv4 resources together, the address resolved by ipv4dns takes precedence.

Screenshot process:

Www.baidu.com screenshot:

Then grab the package and analyze it as follows:

From the above figure, you can see that pc defaults to parsing ipv6 first, and then parsing through ipv4.

The screenshot of resolving the address of Baidu through ipv4 is as follows:

From the screenshot of wireshark, you can see that there is no problem with the accessed resources, that is, there is no problem with subsequent parsing of ipv4.

Www.sina.com.cn screenshot:

From the figure above, you can see that ipv6 is parsed first and then ipv4 is parsed.

Let's take a look at the ipv6 parsing result as shown below:

Ipv6 dns gives you the address above. Among them, 202.106.184.166 is Unicom address, 61.172.201.254 is telecom, 123.125.29.99 is Unicom, and 121.14.1.22 is telecom.

Then we take a look at the address that ipv4 resolved:

The above is the address parsed by ipv4, 218.30.108.232 is telecom.

Then I took a screenshot of tacert www.sina.com.cn on the terminal as follows:

Www.google.com screenshot:

Test results after replacing ipv6DNS:

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