Similarly, the IETF reserves 3 IPv4 /24s, an IPv6 /32 and 2 ASN ranges for that same purpose. [1] https://tools.ietf.org/html/rfc5737 https://tools.ietf.org/ht

Similarly, the IETF reserves 3 IPv4 /24s, an IPv6 /32 and 2 ASN ranges for that same purpose. [1] https://tools.ietf.org/html/rfc5737 https://tools.ietf.org/html/rfc5737 [2] https://tools.ietf.org/html/rfc3849 https://tools.ietf.org/html/rfc3849 [3] https://tools.ietf.org/html/rfc5398 https://tools.ietf.org/html/rfc5398 This also seems to be unknown even to some university professors, who I've seen set up lab exercises using actual CloudFlare ASNs and IPs on a simulator connected to the open Internet. Not exactly dangerous as it would obviously get filtered, but still really bad form.