The Internet can only function as it does by making use of cache technology. A cache is a service (hardware and/or software) that stores data for a defined period. The internet generally contains two types of caches, DNS caches store lookup's for domain names to reduce loading, and web caches often employed by residential ISP's cache webpages to reduce bandwidth.

How Caches Work for DNS:

• When the first customer on an ISP browses to www.gen.net.uk, the ISP's DNS will retrieve the destination server for www.gen.net.uk from GEN's DNS Servers (ns0.gen.net.uk) and return that to the customer.
• When another customer on the same ISP browses to www.gen.net.uk, the ISP uses the already looked up value and returns this to the customer without needing to look it up from GEN's DNS Servers.
• After a pre-defined period (usually 48-72 hours) the cached copy will expire and the next customer on the same ISP that browses to www.gen.net.uk will require the ISP's DNS server to contact GEN's DNS Servers again to get the current destination server.

When you move your site from one VPS to another, then it will take up to 72 hours for all copies of DNS and your site to expire from caches and during this time either the old or new site could be returned. After 72 hours only the new site will be returned.

At GEN when migrating sites from one cluster or platform to another, we always maintain both the old and new site for 72 hours to ensure a site is always returned during the expiry period. When transferring from another service provider, they may not always maintain your hosting during the expiry period unless specifically requested, which we recommend.