CNAME (Canonical Name) is a type of DNS record that is used as an alias for another domain.
DNS (Domain Name System) is a service that translates domain names into IP addresses. Users can easily remember domain names, but computers only understand IP addresses that’s why we need DNS. For example, without this service, you have to type '184.108.40.206' in your browser instead of www.facebook.com to access Facebook. IP - Domain mappings are kept on DNS servers. You can query those matches on securityforeveryone.com
There are two types of IP addresses IPv4, and IPv6. IPv4 address looks like these:
220.127.116.11 127.0.0.1 255.255.255.255
IPv6 addressed looks like these (all of them are the same IP):
::ffff:808:808 0:0:0:0:0:ffff:0808:0808 0000:0000:0000:0000:0000:ffff:0808:0808
CNAME (Canonical Name) is a type of DNS record that is used as an alias for another domain. Let's give a real-life example. You bought a domain such as securityforeveryone.com then you offer an online email service. To do that you've created a new subdomain such as email.securityforeveryone.com. However, you found out that some email clients use the webmail subdomain as default. In that case, you can use a CNAME record to map webmail.securityforeveryone.com to email.securityforeveryone.com. CNAME records must point to a domain name, not an IP address.
Also, another example of using CNAME records is using multiple ports of the same IP addresses. You can use ftp.securityforeveryone.com (21), tomcat.securityforeveryone.com (8080), apache.securityforeveryone.com (80,443) on the same IP addresses. All of them can point to securityforeveryone.com in the CNAME records. With that, when you move your server to another IP address you have to change securityforeveryone.com's A record only.
Simple. Write your domain on the form at the top of the page to check cname records, that's all. Using Security for Everyone’s free cname lookup, you can get cname records and find all cname records for a domain as well as cname record check. Generally, people use CNAME to points to another subdomain or main domain. You can use DNS CNAME lookup tool to get them.
Or if you are using a Linux or an OS X operating system, open the terminal and type dig -t cname yourdomain.com. If your domain has a valid cname record, it would look like that:
dig -t cname securityforeveryone.com ;; ANSWER SECTION: www.securityforeveryone.com. 168 IN CNAME securityforeveryone.com.
If you are using Windows open PowerShell and type Resolve-DnsName -Name yourdomain.com -Type cname.
If you can not see CNAME records that you want, you need to go where you manage the DNS records (usually the hosting provider panel) and check CNAME records. Do not forget that, CNAME records must be a domain name. And must be the only records for the related subdomains.
Also, if your CNAME record shows another domain name, make sure that the domain name is registered by you. If it falls into the hands of malicious people, you may experience a violation of information security.