So I have 100+ websites I manage for various clients, and it is a pain for me to login to their hosting or domain registrar accounts to manage their DNS.
Is there a simple solution, where I can turn on my own server that manages DNS? So for every domain I manage, I simply set a DNS once as ns1…com, and from thereon I can just manage their DNS configurations?
Yes there are a number of solutions out there including running your own bind server. But that is probably a little more difficult than what you might actually want which is just to consolidate their name servers down to one centralized place. Another comment mentioned one, clouddns is another that does this, maybe slightly differently?