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EIGRP autonomous system number

EIGRP supports the autonomous system number range 1 - 65535.

I am looking for the URL that specifies the public range verses the private range. Anyone know of the answer on this?? Tks Frank


Re: EIGRP autonomous system number

Private AS No's are used primarily with BGP, as EIGRP is a "intra AS" protocol there is no real need to assign private AS unless you are planning to talk tot he outside world and your ISP requests you have a 1 to 1 mapping for AS numbers for easier admin etc.

So if you are running EIGRP it will be internal to your network/organisation.


Re: EIGRP autonomous system number

I agree and you are 100% correct - but I had a Cisco document several weeks back that explained the USE of the Private range and the public range. There was something special and different (special situation) where you would use the Private AS vs. the Public AS. If only I knew where I put that URL.

Thanks for the help!!


Re: EIGRP autonomous system number

When customers are multihomed to a single ISP, the ISPs assign private autonomous system (AS) numbers in order to conserve AS numbers.

These private AS numbers come from the range 64512 to 65535. When Border Gateway Protocol (BGP) announces customer prefixes to external neighbors, it needs to drop the private AS number from the path.

This link to ARIN (American Registry for Internet Numbers ) basically says the same thing..:))

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