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Cyclades-PR4000
Chapter 11 - Routing Protocols 109
STEP FOUR
An access list needs at least one rule. The example in Figure 12.6 shows three access lists, each one with
several rules. Each neighbor can be assigned up to 6 access lists, as seen in step 2.
Route Map
Discarded
Routes
Discarded
Routes
Discarded
Routes
Seq. 4
Seq. 10
Access list
popeye_comm
type Community
Access list
popeye_dist
type Distribution
Access list
popeye_path
type AS Path
BGP-4
Message From
Tele Popeye
Seq. 2
Rule 2
Rule 2
Rule 0
Rule 0
Rule 0
Rule 1
Rule 1
Rule 1
FIGURE 12.6 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).