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by mannyv 1004 days ago
One major weirdness with ipv6 is that it occasionally works with ipv4 and it's unclear why.

Example: we run a bunch of endpoints on ipv4, but get ipv6 IPs in our logs. How? Are there 6-to-4 translators out there at ISP edges?

Unknowns in networking are bad.
2 comments
p1mrx 1004 days ago
It's impossible for an IPv4 endpoint to accept an IPv6 connection. Perhaps you have a dual-stack CDN with an unpublished IPv6 address that some users have found? Or your service is accepting third-party 'Forwarded' headers, which would allow HTTP clients to spoof their IP address.
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mschuster91 1004 days ago
> Example: we run a bunch of endpoints on ipv4, but get ipv6 IPs in our logs. How? Are there 6-to-4 translators out there at ISP edges?

Proxies. Your logs are too trusting of X-Forwarded-For headers.

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