I think that’s the nature of unidirectional ip flow. Unless source-based PBR, FBF, or uRPF (iirc, strict) is in use, seems that’s how regular IP works in a unidirectional manner
Aaron > On Aug 19, 2025, at 11:37 AM, Jonathan Kalbfeld via NANOG > <[email protected]> wrote: > > > > > > > This happens unintentionally quite a bit with misconfigured NAT. You will see > RFC 1918 source addresses in packets from time to time. I can't speak to the > application or value of this, but I have seen this and done it accidentally > on one occasion. > > > > > > > > > > > > Jonathan Kalbfeld > > office: +1 310 317 7933 > fax: +1 310 317 7901 > home: +1 310 317 7909 > mobile: +1 310 227 1662 > > ThoughtWave Technologies, Inc. > Studio City, CA 91604 > > https://thoughtwave.com > > > > > View our network at > > https://bgp.he.net/AS54380 > > > > +1 844 42-LINUX > > > > > > > > > > > > > > >> >> On Aug 19, 2025 at 9:34 AM, Sriram, Kotikalapudi (Fed) via NANOG >> <[email protected]> wrote: >> >> >> Question: Can a prefix be never routed on the Internet but used only one-way >> for source address in IP packets? >> >> That is. a user owns an IP prefix. They never advertise a route to it in BGP >> on the Internet. But they use the prefix solely for source address in IP >> traffic from a source to a destination (sink). In this set up, the >> destination server obviously cannot/doesn't return any acknowledgements etc. >> to the source. Anyone aware if there is any such known application in use on >> the Internet - even if it is rare? Thanks. >> >> Sriram >> _______________________________________________ >> NANOG mailing list >> https://lists.nanog.org/archives/list/[email protected]/message/MSEGDFSZ75EMKVD2FWPFSJBOB24X5GQR/ >> > > _______________________________________________ > NANOG mailing list > https://lists.nanog.org/archives/list/[email protected]/message/POV2RZVCP3NZUR7O4WEUA3WKVFRMIKK7/ _______________________________________________ NANOG mailing list https://lists.nanog.org/archives/list/[email protected]/message/4EGLYGWYKABRMQ4I4TO7MIHHHVQCK5ES/
