In this video we will explore how iBGP sessions work. We will focus on the implications of these sessions in terms of next-hop, the advertisements between iBGP sessions, the AS-Path management and synchronization.

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Video Description

The sessions established within the same AS are considered "Internal" (iBGP)
The attributes learned from an iBGP peer are usually not modified (loop prevention)

The AS-PATH is not manipulated within the AS. It's only modified when a prefix is announced from an eBGP session.

The next-hop is not modified when announcement are made to an iBGP peer. 

The routes learned by an iBGP session aren't announced to other iBGP neighbors (loop prevention)

Only the routes learned by an eBGP peer or generated by the router are announced to the iBGP neighbors. Within the same AS, BGP can't ensure a loop free topology using the AS-PATH attribute. Solutions:
Full-Mesh topology 

Synchronization rule: 
Transit will not be provided until all the routers within the AS learn the prefix via an IGP (blackhole avoidance). Solutions:
BGP on all transit routers



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