Enforcing the First AS in BGP AS_PATHs
Curated from Cloudflare Blog
BGP's inherent trust-based model makes it prone to misconfigurations and malicious activity, leading to path leaks or traffic misrouting. The article dives into how enforcing the first AS in BGP AS_PATHs provides a straightforward yet effective defense mechanism against certain types of routing anomalies. While solutions like RPKI offer cryptographic validation, there are scenarios where a more operational approach is needed. This article explains why validating the first AS in the path is a practical step for improving routing integrity. For SREs and network engineers managing BGP announcements, this technique can be an important part of a defense-in-depth strategy. Takeaway: Implement first AS validation at your edge routers to catch and reject suspicious prefixes early in the routing process.
BGP is vulnerable to routing hijacks and path leaks that negatively impact traffic on the Internet. RPKI helps solve some of these problems, but for some forged paths, we need to rely on a simpler mechanism: First AS enforcement in BGP.
— Cloudflare Blog