# IPv6 Limits

[IP addresses](https://www.digitalocean.com/community/tutorials/understanding-ip-addresses-subnets-and-cidr-notation-for-networking) let machines communicate across a network. DigitalOcean Droplets are assigned IPv4 addresses by default. Enabling IPv6 on a Droplet gives you access to its 16 additional IPv6 addresses.

- To use IPv6, it must be enabled and configured at both ends of a connection: where you’re connecting from (like your home or work network) and where you’re connecting to (like a Droplet). Not all ISPs offer IPv6 addresses for customers, so you may not be able to connect to an IPv6 address directly from your local machine.
- We support a maximum of 16 addresses (a subnet mask of `/124`) per Droplet. Additional addresses are not available.
- If the name of an IPv6-enabled Droplet is an FQDN, a PTR record is automatically generated only for the first IPv6 address assigned to the Droplet, not to all 16 addresses available.
- You cannot enable IPv6 on Droplets created from [custom images](https://docs.digitalocean.com/products/custom-images/index.html.md).
- SMTP traffic over IPv6 is blocked at the network level.
- We do not support IPv6 for [VPC networking](https://docs.digitalocean.com/products/networking/vpc/index.html.md).
- IPv6 addresses assigned to a Droplet remain static for the life of the Droplet. Once the Droplet is destroyed, the address is released back into a pool of available addresses in its respective datacenter. Once back in the pool, the chances of obtaining the same address again are unlikely.