I believe IXP networks are usually like this. Globally assigned IPs, and routers can use their IPs on the network to originate ICMP packets (e.g. TTL exceeded during traceroute; or packet too big) but putting a route to the IXP network on the internet is strictly prohibited. On 19 August 2025 20:40:20 CEST, "Jakob Heitz (jheitz) via NANOG" <nanog@lists.nanog.org> wrote:
ICMP packets from internal devices. Example “unreachable”.
Kind Regards, Jakob
---------------------------- 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
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