BGP 4-Byte ASN Format Converter

This tool will help you convert 4-Byte Autonmous System Numbers between the ASDecimal (123456) and ASDdot (1.57920) formats. You can refer to our post on 4-Byte BGP ASN here for more details.

Convert BGP 4-Byte ASPlain format to ASDot+:

ASDdot is:

Convert BGP 4-Byte ASDot format to ASPlain:

ASPlain is:

What is BGP 4-Byte ASN?

The 2 byte format allowed for 65,535 different AS numbers (2^16). The new 4-byte format allows 4294967295 different AS numbers (2^32). The numbers from 0 to 65,535 are common between the two formats allowing for easier interoperability. The 4-byte format is represented in one of three ways called the asplain, asdot+ and the asdot. Refer to the RFC5396 for explanation of these representations.

What is 4 bytes ASPlain format?

Asplain is the most simple to understand, these are just regular decimal numbers. For example, AS number 545435, 4294937295, 4254967294, 2294967295, etc. These numbers are simple to understand but prone to errors. It’s easy to make a configuration mistake or misread a number in the BGP table.

What is 4 bytes ASDot+ format?

Asdot+ breaks the AS number in two 16-bit parts, a high-order value, and a low-order value, separated by a dot. All older AS numbers can fit in the second part where the first part is set to 0.