Establishing the Need for iBGP with Two Internet-Connected Routers
Two Internet-connected routers in an enterprise need to communicate BGP routes to each other, because these routers might want to forward IP packets to the other Internet-connected router, which in turn would forward the packet to the Internet. With an iBGP peer connection, each Internet-connected router can learn routes from the other router and decide whether that other router has a better route to reach some destinations in the Internet. Without that iBGP connection, the routers have no way to know whether the other router has a better BGP path.
For example, consider Figure 14-2, which shows two such cases.
Figure 14-2 Choosing the Best Routes from ASN 11 to 181.0.0.0/8 ...
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