Cyclades-PR2000
STEP FOUR
An access list needs at least one rule. The example in Figure 9.6 shows three access lists, each one with several rules. Each neighbor can be assigned up to 6 access lists, as seen in step 2.
Discarded | Discarded | Discarded |
Routes | Routes | Routes |
BGP-4
Seq. 10 | Seq. 4 | Seq. 2 | Rule 1 | Rule 0 | Rule 2 | Rule 1 | Rule 0 | Rule 2 | Rule 1 | Rule 0 |
Message From
Tele Popeye
Route Map | Access list | Access list | Access list |
| popeye_comm | popeye_dist | popeye_path |
| type Community | type Distribution | type AS Path |
FIGURE 9.6 UPDATE MESSAGE ARRIVING FROM TELE POPEYE PASSING THROUGH 3 FILTERS AND A
ROUTE MAP
An update message arriving from the neighbor called Popeye in step 2 will pass through the filters assigned to it in the Neighbor Menu. The figure shows the case where the scope of the list is permit and that of the rules is deny. Each rule causes routes to be discarded until finally the shortened message arrives at the route map (if one has been configured for this neighbor).
Chapter 9 - Routing Protocols | 82 |
