In the BSCI Certification Guide they have the following config.
ip summary-address eigrp 100 172.xx.x.0 255.255.224.0
ip summary-address eigrp 100 0.0.0.0 0.0.0.0
the ip summary-address is to summarize the networks 172.xx.x.0/24 - 172.xx.xx.0/24 back towards the core of the network right?
The guide says "Thus the division is summarized to the larger network and receives back a simple default route."
What does that mean? I can understand the summary address being placed in the routing table and matching any destination in 172.xx.x.0 /19 but how does the default route get matched? Does 0.0.0.0 get installed in the local route table or advertised to other routers?
Sorry it does not have a diagram and it is just confusing me.
It also states: "Summarizing the default route can be a useful technique. However, if used in cases where there are multiple default paths, this will reduce routing options and prevent fail over to alternate paths when the primary path fails."
I don't understand that statement either. We don't have EIGRP at work and I am trying to learn it.