I just came back from full blown forensics mode. Conclusion: everything OK, this was just caused by multiple levels of (third party) stupid.pic.twitter.com/C2kjhAs2I4
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Apparently they're using RFC1918 space for CgNAT (which is stupid, they should use RFC6598) and it leaks into their colo servers sans NAT.
Remember that all IPv4 address space is routable. RFC 1918 is usually not routed. (127/8 is debatable.)
Nice find. :-)
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