Lately, Cisco has been recommending a departure from the classic hierarchical campus design model to include a routed access layer instead of a switched access layer.
In this new model, it is recommended that the routed access layers (if they are using EIGRP as the core IGP), should be configured as EIGRP stubs, meaning that the access switches will never be queried for reachability information for any networks EXCEPT for the networks it is directly connected to and which it is advertising to the distribution layer. In other words, the access layer switches should never be treated as transit points for traffic to pass through on its way to somewhere else. So, the access layer routed switch will advertise itself as an eigrp stub and the distribution switches will oblige by never querying them for any networks that it is not directly connected to.
Secondly, a route filter in place at the distro switches which will ensure that the routed access switches ONLY receive a default route, is the complement of the eigrp stub design. In other words, the access switch says, "look, I am ONLY connected to these networks and I am NOT to be treated a transit point to get to anywhere else, so NEVER ask me about how to get to any network, EXCEPT for the ones to which I am directly connected."
In turn, the distro switch says, "Fine, I wont ask you for any inpofmration on any networks, EXCEPT for the ones to which you are directly connected, and furthermore, I dont want you to ask me about any specific routing information. I will ONLY advertise a default route to you and you should just send me all your traffic, period."
This way, the routing convergence process between distro and access is minimized and mitigated. And rightfully so, given the topology.
So, here is my question: couldnt all this have been achieved with static routes? Place a static default route in the access switches pointing to the distro, which is exactly the effect that dynamically advertising a default from the distro has on the access switches' routing table. In other words, dynamic or static, either way, the aqcces switche sare going to have ONE route in the routing table -- the default route pointing to the distro.
Furthermore, if, say, the access switches are directly connected to networks A, B, C, and D, why not simply install 4 statics in the distro switches and redistribute them back to the rest of the enterprise?
Why do I ask this? because it seems that in the document, there is this great concern to minimze convergenece time and minimize protocol back plane protocol exchanges between distro and access. Well, if thats the big worry, just go static and get rid of all those routeing protocol-induced worries. NO???