How it works
IPv6 uses a much larger address space than IPv4 and a different packet format. A network can run both protocols together when the provider, router and devices support them. Addresses have different purposes, including local-link communication and globally routed traffic; seeing an IPv6 address on a device does not alone prove internet connectivity.
Important differences and limits
IPv6 is neither automatic encryption nor a substitute for firewall rules. A device may receive a globally routable address while unsolicited incoming traffic remains filtered. DNS, provider routing and changing address prefixes can affect reachability. IPv4 port-forwarding rules do not automatically define the equivalent IPv6 policy.
A useful practical check
Check provider support, router configuration and successful connectivity on a real client. Test important applications on both protocols if they support both. Review the router’s IPv6 firewall rather than disabling it to make a service work. When troubleshooting, distinguish address assignment, name resolution and routing instead of treating all IPv6 issues as one fault.
An example in practice
An IPv6-capable website and an IPv4-only service can take different network paths from the same device. If only one fails, record which protocol was used. That distinction directs investigation toward routing, DNS or filtering rather than assuming the whole connection is unavailable.