Explaining 4-Octet Autonomous System (AS) Numbers for Cisco IOS

This paper explains the changes the 4-octet AS has for the BGP routing infrastructure. It will also explain some technical and operational differences between the traditional 2-octet and 4-octet AS BGP technology. This paper will also explain configuration specific aspects in relationship to 4- octet AS systems. This paper provides a technological overview to explain why the Internet will migrate to using the 4-octet AS system; the paper also explains the working principles and provides insight on configuration aspects of a 2/4-octet system. The Cisco IOS 4-octet Autonomous System support is fully backward compatible with the traditional 2-octet Autonomous System and provides a reliable and proven path for next generation Internet infrastructure.