Better Source of Information
Routes learned from eBGP peers have an administrative distance of 20, and routes learned from iBGP peers have an administrative distance of 200. Why the huge difference? BGP is designed to share routes between different autonomous systems. Therefore, if you learn a route from another autonomous system via eBGP, iBGP, or EIGRP sources, you want the eBGP-learned route to be the best source of information over all the other dynamic routing protocols. For example, refer to Figure 18-5 again. R1 advertises 10.1.1.0/26 to R2 using eBGP and R3 using eBGP. R3, because it has an iBGP peering with R2, advertises it to R2 using iBGP. In addition, let’s say on R3 we redistribute the 10.1.1.0/26 eBGP-learned route into EIGRP and ...
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