BGP route processing

FIGURE 8 . 9 BGP route processing
1. The BGP speaker receives the BGP routes.
2. The received BGP routes are placed in the Adj-RIBs-In.
3. The BGP routes are sent to the inbound policy engine.
4. The inbound policy engine filters and manipulates routes based on the policy set by the
router’s administrator. BGP routes that are filtered out by the inbound policy engine are
dropped at this point.
5. The remaining BGP routes are then forwarded to the Loc-RIB.
6. The BGP speaker stores the routes in the Loc-RIB. The router uses these routes to make
BGP routing decisions.
7. The BGP routes are then forwarded to the outbound policy engine.
8. The outbound policy engine filters and manipulates routes based on the policy set by the
router’s administrator. BGP routes that are filtered out by the outbound policy engine are
dropped at this point.
9. The BGP routes that make it through the outbound policy engine are then forwarded to the
Adj-RIBs-Out.
10. The received BGP routes are then stored in the Adj-RIBs-Out.
11. All BGP routes stored in the Adj-RIBs-Out are then advertised to all of the BGP
speaker’s peers.
With an understanding of the function of all the different RIBs, let’s take a look at how all
of this fits into the decision process of a BGP speaker.