By default, what is the valid AS number range for a BGP process on a Cisco router?
- 1 to 256
- 1 to 32,768
- 1 to 65,535
- 1 to 131,072
Explanation: Autonomous Systems are identified by AS numbers, which are defined as 16-bit integers. This results in a valid range from 1 to 65,535.
Within this 16-bit range, numbers are categorized by their usage:
- Public AS numbers: These range from 1 to 64,511 and are assigned and managed by the Internet Assigned Numbers Authority (IANA).
- Private AS numbers: These range from 64,512 to 65,535 and are reserved for customers who need to run BGP within their private networks.
The sources also note that while 32-bit AS numbers were later created to address pool exhaustion, the standard 16-bit integer representation remains a fundamental part of BGP identification.
Related exam: Modules 8 – 13: Checkpoint Exam: Network Routing Answers (CCNP ENCOR v9)
