Discard route Null0

Hello Experts,

When summarising routes in OSPF a discard route to Null0 is automatically
created on ABR where summarisation is performed. For example:

O 1.1.0.0/22 is a summary, 00:00:02, Null0
O 1.1.1.0/24 [110/65] via 10.1.12.1, 00:00:02, Serial1/0.21
O 1.1.2.0/24 [110/65] via 10.1.12.1, 00:00:02, Serial1/0.21
O 1.1.3.0/24 [110/65] via 10.1.12.1, 00:00:02, Serial1/0.21

I am reading in my workbook that a Null0 route purpose is to stop forwarding
loops. Can anyone please explain how this loop prevention works ? Why then
there is a command to remove the Null0 route ? In the lab I do what I am
told but in the real life is there a reason to remove a Null0 route ?

Thanks,

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Received on Sun Aug 01 2010 - 01:48:27 ART