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Implementing Cisco Networking Solutions by Harpreet Singh

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BGP

Large organizations have pubic IP address blocks assigned to them from their regional address registries. Such organizations also have something known as an Autonomous Number, commonly known as ASN, which they use as their identifier to the internet.

Assume an organization that has an IP address block of 200.80.80.0/22 allocated to it, and has an ASN of 1000. This organization can connect to two or more upstream providers using BGP as the routing protocol, and can advertise the /22 prefix to any of the upstream providers. The advertisement of the prefix would control the incoming traffic from the upstream ISP into the organization. The internet generally takes the shortest number of AS hops from source to the destination, and therefore ...

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