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Autonomous System (Internet)In the Internet, an autonomous system (AS) is a collection of IP networks under control of a single entity, typically an Internet service provider or a very large organization with redundant connections to the rest of the Internet, that adhere to a single and clearly defined routing policy. A unique AS number (or ASN) is allocated to each AS for use in BGP routing. The numbers are assigned by the same authorities that allocate IP addresses. AS numbers are currently 16-bit integers. There are public numbers, which may be used on the Internet and range from 1 to 64511, and private numbers from 64512 to 65535, which can be used within an organization. Types of AS: - Multihomed AS
- Stub AS
- Transit AS
AS numbers are allocated to the regional registries by the Internet Assigned Numbers Authority (IANA, http://www.iana.org). From the IANA website, http://www.iana.org/assignments/as-numbers, we get this information on which ASN blcoks are assigned to which regional registries, as of February 10, 2005: AUTONOMOUS SYSTEM NUMBERS Number Description
------------------------------------------------------------- 0 Reserved - May be use to identify non-routed networks 1 - 1876 Allocated by ARIN 1877 - 1901 Allocated by RIPE NCC 1902 - 2042 Allocated by ARIN 2043 Allocated by RIPE NCC 2044 - 2046 Allocated by ARIN 2047 Allocated by RIPE NCC 2048 - 2106 Allocated by ARIN 2107 - 2136 Allocated by RIPE NCC 2137 - 2584 Allocated by ARIN 2585 - 2614 Allocated by RIPE NCC 2615 - 2772 Allocated by ARIN 2773 - 2822 Allocated by RIPE NCC 2823 - 2829 Allocated by ARIN 2830 - 2879 Allocated by RIPE NCC 2880 - 3153 Allocated by ARIN 3154 - 3353 Allocated by RIPE NCC 3354 - 4607 Allocated by ARIN 4608 - 4864 Allocated by APNIC 4865 - 5376 Allocated by ARIN 5377 - 5631 Allocated by RIPE NCC 5632 - 6655 Allocated by ARIN 6656 - 6911 Allocated by RIPE NCC 6912 - 7466 Allocated by ARIN 7467 - 7722 Allocated by APNIC 7723 - 8191 Allocated by ARIN 8192 - 9215 Allocated by RIPE NCC 9216 - 10239 Allocated by APNIC 10240 - 11263 Allocated by ARIN 11264 - 12287 Allocated by ARIN 12288 - 13311 Allocated by RIPE NCC 13312 - 14335 Allocated by ARIN 14336 - 15359 Allocated by ARIN 15360 - 16383 Allocated by RIPE NCC 16384 - 17407 Allocated by ARIN 17408 - 18431 Allocated by APNIC 18432 - 19455 Allocated by ARIN 19456 - 20479 Allocated by ARIN 20480 - 21503 Allocated by RIPE NCC 21504 - 22527 Allocated by ARIN 22528 - 23551 Allocated by ARIN 23552 - 24575 Allocated by APNIC 24576 - 25599 Allocated by RIPE NCC 25600 - 26623 Allocated by ARIN (March 2002) 26624 - 27647 Allocated by ARIN (September 2002) 27648 - 28671 Allocated by LACNIC (November 2002) 28672 - 29695 Allocated by RIPE NCC (December 2002) 29696 - 30719 Allocated by ARIN (March 2003) 30720 - 31743 Allocated by RIPE NCC (September 2003) 31744 - 32767 Allocated by ARIN (November 2003) 32768 - 33791 Allocated by ARIN (May 2004) 33792 - 34815 Allocated by RIPE NCC (June 2004) 34816 - 35839 Allocated by RIPE NCC (February 2005) 35840 - 36863 Allocated by ARIN (February 2005) 36864 - 48127 Held by the IANA 48128 - 64511 Reserved by the IANA 64512 - 65534 Designated for private use (Allocated to the IANA) 65535 Reserved Specially designated Autonomous System Numbers: 23456 AS_TRAN draft-ietf-idr-as4bytes-04.txt []
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