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JUNOS Enterprise Routing by Harry Reynolds, Doug Marschke

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BGP and the Enterprise

The preceding section provided a targeted review of BGP’s operational characteristics and scaling approaches. BGP is normally associated with Internet service provider (ISP) networks that offer transit services for Internet traffic. This section focuses on how BGP can be applied to meet the routing needs of enterprise networks.

When Should an Enterprise Run BGP?

BGP is a sophisticated routing protocol that can help to optimize an enterprise’s routing, but that doesn’t mean all enterprise networks will see a benefit from its deployment. An enterprise decision to run BGP normally hinges on the benefits that can be gained by making intelligent outgoing routing decisions and by using BGP attributes in an attempt to influence how upstream networks route toward your network to help control which links are used for ingress traffic. The common factor to both of these scenarios is a network with at least two external connections—such a network is considered to be dual-homed. Enterprise networks with a single attachment to a service provider will normally not benefit by running BGP and should simply use a static default route. When dual-attached to the same provider, two static defaults can be used to achieve some measure of outbound load balancing.

A word about AS numbers

Although likely obvious by now, we must state that to run BGP you must first have an AS number. Like IP addresses, there are both public and private AS number pools. Public AS numbers are assigned by ...

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