On 5 Aug 2025, at 00:53, Yang Yu <[email protected]> wrote: > In 5. Best Practices > >> Don't prepend ASNs that you don't own > > Should the language here be stronger and expand a bit why doing so is > a bad idea.
In the long, distant past I have had a reason not to follow this advice. This is long enough ago that surely I can reveal my cowboy antics without upsetting any current operators. The situation was related to the origination of a route from a New Zealand network that we definitively did not want to propagate through North American networks towards Telstra in Australia (we originated the route towards Telstra over different paths across the Tasman). There were covering aggregates to protect against reachability. I prepended 1221 to the routes I went towards US providers for the purpose of poisoning those routes and making them unacceptable to 1221 routers who might otherwise learn them. This was effective. It served a purpose. It wasn't malicious and it wasn't intended to impersonate anybody or hijack anything. The 1221 people knew I was doing it, and perhaps they had given up complaining about my shenanigans by that point but they didn't tell me to stop. I have always thought of AS_PATH as a loop avoidance mechanism, and that's precisely how it was being used here. Was it wrong? Was it a bad idea? If you (collectively) think yes, can you say why? Joe _______________________________________________ GROW mailing list -- [email protected] To unsubscribe send an email to [email protected]
