I have a website which has recently migrated to a new server. The old server has a proxy_pass in place in the nginx config to ensure any requests that land there due to old DNS get routed to the new server.
It's been a few days now and I'm still seeing some traffic hitting the old server in the access log.
Is there a particular header that could be added to the response served from the old server to indicate that the IP for that host should be refreshed? Perhaps a Cache-Control: no-cache or Expires? Or maybe a header which indicates the new IP?