:Alibaba Cloud DNS FAQ

Questions

• Why is my domain name inaccessible?
• How do I know whether my domain name resolution is in effect after modification?
• After I change my DNS servers at the registrar, how long does it take for the resolution record to take effect?
• Why is the IP address obtained by pinging the domain name different from the resolution record?
• Why cannot my website be opened using the domain name, but can be opened using the IP address or other domain names?

Why is my domain name inaccessible?

A domain name may become inaccessible for reasons including failing to perform real-name registration, or failing to file the domain name record.

You can view domain states using Alibaba Cloud’s whois search function. A domain becomes inaccessible if it is in one of the following states:

• Pendingdelete (domain expired or under redemption)
• Redemption period (domain expired or under redemption)
• Clienthold (domain frozen)
• Serverhold (domain frozen)
• Inactive (no DNS configured)

How do I know whether my domain name resolution is in effect after modification?

The resolution records of a domain name can be modified at the DNS provider. Both the recursive DNS and the authoritative DNS can affect how resolution records take effect on the user side.

If a problem is detected, you can perform the following tests to identify the problem:

1. Test whether the resolution record takes effect on the recursive DNS. The operations are as follows:

   • For Windows users:

     1. Select Start > Run. Enter cmd and press Enter to open the CMD command line.

     2. Enter nslookup "domain name to be tested" and view the result.

     

2. Test whether the resolution record takes effect on the authoritative DNS. The operations are as follows:

   • For Windows users:

     1. Press CTRL+R to open the Run window. Enter cmd and press Enter to open the CMD command line.

     2. Enter nslookup "domain name" "DNS server address" and view the result. The DNS servers of Alibaba Cloud advanced DNS are: vip1.alidns.com and vip2.alidns.com.

     

   • For Mac or Linux users:

     Open the terminal controller. Enter dig "domain name" "@DNS server address" and view the result. The DNS servers of Alibaba Cloud advanced DNS are: vip1.alidns.com and vip2.alidns.com.

     

Results

• If the resolution record does not take effect on both the recursive DNS and the authoritative DNS, the domain name has not been successfully added.

• If the resolution record takes effect on the authoritative DNS but does not take effect on the recursive DNS, the domain name resolution, after being successfully added, is not yet synchronized to the global recursive DNS.

  Repeat the preceding test after the TTL of the domain name expires. If the resolution record continues to not take effect on the recursive DNS, the domain name may be hijacked or the DNS cache may be being attacked by a virus.

If I change my DNS servers at the registrar, how long does it take for the resolution record to take effect?

Depending on the type of suffix, it may take up to 48 hours for domain name resolution to take effect on the new DNS server, and to be fully synchronized to global DNS. During the DNS server switchover period, some DNS query requests are directed to the new DNS server, while others continue to be directed to the old server. You must ensure that the domain name record is the same on the new and old DNS servers, and do not perform any operations during the DNS switchover period. If the domain name resolution does not take effect, check whether your DNS server is changed during the 48/24 hours.

Different suffix cache times are detailed as follows:

• The DNS cache time for .com is 172,800 seconds (48 hours).
• The DNS cache time for .cn is 86,400 seconds (24 hours).
• The DNS cache time for .net is 172,800 seconds (48 hours).

Why is the IP address obtained by pinging the domain name different from the resolution record?

The following scenarios may have occurred:

• Before the changed domain name record takes effect on the recursive DNS, the IP address obtained by pinging the domain name remains that same as that of the IP address mapped to the old domain name. After the TTL of the domain name expires, ping the domain name again. If the IP address remains unchanged, the carrier’s DNS may have been hijacked.

• If the domain name change fails, it is possible that the domain name has failed to be properly configured on the authoritative DNS, or the DNS server maintaining the domain name was recently changed.

Why is my website not opening with my domain name, but can be opened with the IP address or alternative domain name?

If the IP address resolved by the DNS server is the same as the domain name’s resolution record, the problem comes from network connection and Web server processing. You can:

• Run the ping command to test network connection.
• Check whether the host configuration of the Web server is correct.
• Check whether the accessed domain name is added to the whitelist of the firewall if a web firewall is installed.