Task 5.3 - AS Path Prepending As Opposed To Filter

Just a question, in task 5.3, AS400 is supposed to route through AS300 to get to VLAN3. The SG shows AS path prepending to make the path less preferred through R5 than through R2. Why not to cause R1 to filter advertising VLAN3 to R5? Thanks in advance.


  • bentlym,

    If you filter the route advertisement to eliminate one of your gateways, the routes will be unreachable if that gateway or link goes down. By creating a preference for one route, while still advertising the less preferred route, the network will still be reachable if one link or router goes down.

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