Why does BGP need an IGP within an AS to function?
One of the prerequisites to deploying BGP is the fact that you need to have fully functioning routing within an Autonomous System before you can deploy BGP. In other words, in order for internal BGP (iBGP) to operate, you must deploy an Interior Gateway Protocol (IGP) such as EIGRP or OSPF to ensure routing is established. This however can be counterintuitive. Since we're deploying BGP, which is itself a routing protocol, why do we need another routing protocol to make it work? In this video, I'll explain the reasoning behind this seemingly illogical logic.
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