Dynamic DNS is where the router is always allocated a dynamic IP address by the ISP. The router then contains software which works with specific third party organisations, who control their DNS records. The router monitors the existing IP address given by the ISP and advises the Dynamic DNS provider of any changes to the IP. The Dynamic DNS provider then publishes any change in the users IP via it’s DNS servers. The customer must have their SOA for their domain name registered with these Dynamic DNS providers, or alternately have a subdomain registered with them.
Most dynamic DNS providers offer an option for hosting yourcompany.com for a fee, or yourcompany.DNS2Go.com for free. If you register your domain name through a register that will let you manage your own info (instead of the ISP or web host) then you can
direct yourcompany.com and your MX records to yourcompany.dns2go.com,and get the functionality and retain the ability to make changes.