Static Route to Null 0 for summarization

Could you;ll please explain the "Static Route to Null 0" concept in summarization, in much more depth.I would highly appreciate it you'll explained it using an example/diagrams/IP addressing . I referenced Cisco 's example at :

but yet have my doubts about it..


  • Let us assume the route to NULL0 is not created. RouterA connects to RouterB. RouterA is advertising a summary ( to RouterB. RouterA also has a default route pointing to RouterB. RouterB sends a packet destined for to RouterA. RouterA does not have this subnet in the routing table. It forwards the traffic back to RouterB using the default route. RouterB then forwards back to RouterA and we have a loop.

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