Now we're going to talk about separation of iBGP vs. eBGP. Many ISPs do not understand the importance of separating iBGP and eBGP. Remember that iBGP is where all customer prefixes are carried. eBGP is used for announcing aggregates to the internet and for traffic engineering. Do not do traffic engineering with customer originated iBGP prefixes, as this leads to instability to that mentioned in the earlier bad example. Even though the aggregate is announced, a flapping subprefix will lead to instability for the customer concerned. Traffic engineering prefixes should always be generated on the border routers.

© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.

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