When should EIGRP automatic summarization be turned off?

Question

1. when a router has not discovered a neighbor within three minutes
2.when a router has more than three active interfaces
3.when a router has discontiguous networks attached
4.when a router has less than five active interfaces

Answer 1

Answer 3. Auto summarization is on by default. When you have disconnected subnets and need to route between them, you need to use the "no auto-summary" EIGRP command to turn off autosummarization. This way you will send the subnet information across the classful network boundaries.