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5. What is a "NAS"?

"NAS" stands for "Network Access Server". A Network Access Server is a device which usually has interfaces both to the backbone and to the telco (POTS or ISDN) and receives calls from hosts that want to access the backbone by dialup services. A NAS is e.g. located at an internet provider's point of precence to give their customers internet access.

The most commonly used protocol is PPP, especially IP oder PPP.

Examples for NASs from Cisco include the special-purpose AS5200, AS5300 and AS5800 as well as general-purpose routers like the 4000 oder the 3600 series.

The NAS contacts the TACACS+ or RADIUS daemon to makes authentication and authorization requests and send accounting packets. The other direction is not possible.


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