EIGRP Stub Routers - Conflicting explanations in training materials

In Chris Bryant's materials, he explains that on a hub and spoke network, that the multiple spoke routers should be configured as Stubs, advertising their connect / summary routes and receiving a default route as the single next hop from the Hub.

Another, better explanation I found on youtube said that it is best to make the Hub on a Hub-and-Spoke topology the Stub, as it is the 'end of line' router and will have no upstream routers to Query for a route that it isn't already advertising. Basically the explanation was, "If a router is at the end of an Area with no upstream routers for DUAL Query packets to be sent to, it does not need those DUAL Query's being sent to it at all.

In fairness to the first vs second explanation, Chris Bryant's example did not connect the Spoke routers at all via a LAN segment to exchange information, whereas the second one did (not sure if that makes a whole lot of difference as I've had to make LAN interfaces passive to avoid adjacencies dropping).

Was anyone else confused about this, or have any kind of explanation what characteristics really underscore which router should be Stub(s)?

Both explanations above make decent points that none of the routers in either scenario have neighbors to query, but one is saying Stub the Hub and the other is saying Stub all the Spokes - Any help on this is greatly appreciated!

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Comments

DCD

I'm curious what video that was. You want to do the spokes as stubs because they won't have a route to other networks.

joetest

Ask yourself; What does the Stub feature actually do - what is it used for?

And what would happen if you put it on the hub? You should lab it out and see what happens. Notice the routing tables on the spokes

Danielh22185

joetest wrote: »

Ask yourself; What does the Stub feature actually do - what is it used for?

And what would happen if you put it on the hub? You should lab it out and see what happens. Notice the routing tables on the spokes

This is a great answer! In these types of situation when I am trying to decipher an explanation in a video or book, or trying to understand it better for myself, I lab it! I think you will quickly find out and develop a better understanding once you lab it up!

ande0255

Below is the youtube video that shows that it should be configured on the Hub router, when my training materials show that it should be configured on the Stubs. I am not sure if it's because this youtube video is showing a LAN connecting the stubs, or why the Hub is being configured here?

https://www.youtube.com/watch?v=AZ4XzZ4QZ_M

Danielh22185

ande0255 wrote: »

Below is the youtube video that shows that it should be configured on the Hub router, when my training materials show that it should be configured on the Stubs. I am not sure if it's because this youtube video is showing a LAN connecting the stubs, or why the Hub is being configured here?

https://www.youtube.com/watch?v=AZ4XzZ4QZ_M

@2:36 he explicitly says "you only enable it on the stub router itself" (R5). I think you might be confusing that R5 is the hub router but his topology has two hub routers at the top of the topology connecting to R5.

Like I mentioned, lab it! This is a great scenario for something like this and would take literally minutes to setup.

Danielh22185

On a side note I wish there were more active CCIE youtubers..

ande0255

I'm curious as to how you determine those are two hubs running to a single spoke (unless I missed him say that), as the terminology he uses I could see you coming to that conclusion with the home office / branch site, but in study materials hub and spoke seems like usually at least 1 hub connecting to at least two spokes. That's why this has been a struggle for me to wrap my head around, I get it should be applied to end of line routers, but how would you determine R5 to be the single spoke for two hubs? Or was it indeed the home office / branch office terminology?

Danielh22185

I think you are thinking too single connection oriented. Having multiple hubs for a remote / stub site is actually very common. Honestly I think his example is pretty spot on...

james43026

He does indeed say that the router 5 is dual homed to router 2 and router 4, and R2 and R4 are both connected to the same network / networks.