1
Diagnostic step 1
Check each client for an IPv4 address (ipconfig /all or ip -4 addr). If clients lack IPv4, confirm whether that was intended and whether NAT64/DNS64 is configured on the router.
FULL AI ANALYSIS
IPv6-only home network times out on IPv4-only websites after switching to DHCPv6-only LAN
Generated Oct 3, 2026, 12:35:03 AM
Analysis summary
Symptoms point to a LAN that has become effectively IPv6-only for client addressing while Internet content remains a mix of IPv4-, IPv6-, and dual-stack-only sites. Clients resolve IPv4 addresses but lack an IPv4 path because IPv4 addressing/NAT or router rules no longer apply to current client addresses. Working-by-enabling-IPv4-DHCP-on-a-client indicates the issue is local to how the LAN is provisioned or NATed rather than the upstream ISP completely blocking IPv4.
Possible causes
LAN moved to IPv6-only addressing (clients have IPv6 but no IPv4 addresses) while router NAT/masquerade configuration still expects IPv4 LAN addresses.
95%Firewall rules on router are filtering IPv4 traffic from current client addresses or lacking an IPv4 source NAT rule for new addressing.
90%Missing or misconfigured NAT64/DNS64 service if the intention was IPv6-only LAN to reach IPv4-only destinations.
20%ISP provides IPv6-only WAN without provisioned NAT64/DNS64 and some sites are IPv4-only, requiring IPv4 fallback on LAN.
5%Suggested fixes
2
Diagnostic step 2
On the router, verify IPv4 masquerade/NAT rules apply to the active LAN subnet(s). If you disabled DHCPv4, ensure NAT rules don't reference the old subnet address space.
3
Diagnostic step 3
Temporarily re-enable IPv4 DHCP for a small test group (as you did) to confirm persistent reachability; this is reversible and helps isolate whether IPv4 addressing is the issue.
4
Diagnostic step 4
Capture packet traces on the router during a failed IPv4 connection (tcpdump -i <iface> host <client-ip> and host <v4-dest>) to confirm whether SYN packets leave the LAN and whether replies return.
5
Diagnostic step 5
If you intend to operate IPv6-only on LAN, deploy and test NAT64/DNS64 (e.g., tayga/jool + a DNS64-capable resolver) in a lab first; otherwise plan to restore dual-stack DHCPv4 until a translation service is in place or ISP provides IPv4 connectivity guarantees.