Autonomous System Numbers are closely related to BGP. Each of the autonomous systems that make up the global network that constitutes the internet has a unique identifier, that is, the ASN. Edge routers are configured manually with a combination of the ASN and IP address of peer routers. In many of the recipes in this book, we use the default private ASN (usually 65,000), but if your organization has a public ASN, you will want to make sure you configure your VPN using that number.