Hello there--one of my clients is also seeing this beginning Monday. Rebooting the comcast router seems to stop it for a while. It seems to be that IPv6 addresses are being handed out but not IPv4. Static IPv4 addresses with static DNS entries are fully functional. Expanded the DHCP range as well.
IP Address Lookup / IPv4 / IPv6 - IP.SB IPv4 Address Lookup, IPv6 Address Lookup. IPv4 connectivity IPv4: Unkown: Address: Hostname: ISP: IP Organization: ASN: ASN Organization IPv6 - Wikipedia Renumbering an existing network for a new connectivity provider with different routing prefixes is a major effort with IPv4.   With IPv6, however, changing the prefix announced by a few routers can in principle renumber an entire network, since the host identifiers (the least-significant 64 bits of an address) can be independently self IPv6 No Network Access: Everything You Need to Know and
Mar 26, 2020
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IPv4 vs IPv6 | Top 9 Most Useful Differences You Need To Know
IPv4 vs IPv6: What's the Difference?| IPv4 or IPv6 for