How do the addresses differ?
IPv4 uses 32 bits, allowing 2³² addresses, approximately 4.3 billion. IPv6 uses 128 bits, allowing 2¹²⁸ or about 3.4 × 10³⁸ addresses. Not all are publicly usable: both protocols reserve special-purpose ranges. IPv6 can abbreviate consecutive zero groups with ::, at most once per address.
NAT and automatic configuration
IPv4 networks often use NAT to share public addresses, but IPv4 does not require NAT. IPv6 normally does not need NAT for address sharing. Addresses can be configured manually, through DHCP for IPv4, and through SLAAC or DHCPv6 for IPv6. IPv6 default gateways are learned through Router Advertisements.
Is IPv6 safer or faster?
IPv6 does not automatically encrypt traffic. IPsec can be used with either protocol. Globally addressed IPv6 devices still need firewall protection. Performance depends on routing, provider and destination. IPv6 uses multicast instead of broadcast and a fixed base header; additional features can require extension headers.
Dual stack and practical tests
IPv4 and IPv6 are distinct protocols. Dual stack runs both in parallel. Working IPv4 does not guarantee IPv6 connectivity. Check DNS A and AAAA records and test each connection separately. Server-side ipcheck.tools tests describe connectivity from the server in Düsseldorf to the destination.