Exam 300-420 topic 1 question 10 discussion

should be A. R1 has no route to R2 and drops the traffic Stub router only advertise Connected and Summary - it will not re-advertise route

I've studied this topic in depth. The correct answer is A By default when you setup an EIGRP Router as a STUB it will advertise connected routers and summary routes only as a default behavior, however, it will NEVER advertise learned EIGRP routes learned from neighbors, in this case Hub 2 it's the destination. The question answer will be found at the end of the question itself where it says What happens when R1 is trying to send a packet to a SUBNET attached to R2, this is not gonna happen because the Stub Router only advertise directly connected and summary routes to the Hub. By the way, R1 (Hub) won't even bother sending queries to R3 stub router either which also makes this answer correct. This answer can be found on the OCG Book Page 147 & 148, if you take time reading it you'll find it. This feature is cool but be careful and read it carefully.

Mocked up the scenario in the lab, A is correct.

The EIGRP stub routing feature can prevent this problem by preventing the remote device from advertising core routes back to the distribution devices. In the above example, routes learned by the remote device from distribution router 1 will not be advertised to distribution router 2. Therefore, distribution router 2 will not use the remote device as a transit for traffic destined to the network core

Just labbed this .. if on default - connected summary it installs the directly connected route on R1s table for R3. The only time it removes the next-hop R3 is you use the strcitest stub command which "receive-only" but the question does not say if one should use receive only on c+S

A is correct, but the question is how to reach R2. We already know that it will be drop base on the scenario presented that means the next step is to forward it to R3 to reach R2. ill go with D.

A is correct 300-420 Cert Guide - Chapter 3 "Routing Protocol Characteristics, EIGRP, and IS-IS" page 111 EIGRP Design > EIGRP Stub Routers "When the stub routing feature is enabled on the spoke router, the router only advertises specified routes to the hub router. The router does not advertise routes received from other EIGRP neighbors to the hub router. The only disadvantage is that the stub router cannot be used as a backup path between two hub sites." Being that the link between R1 and R2 has failed, the only routes that R1 will now know about are from R3. But remember, R3 will not advertise routes that it has learned from other routers (R2). So R1 will not know any routes from R2.

Stub routers cannot act as transit

Stub mode does not transit

I agree. A is correct. Stub routers can't be used as a backup path between two hub sites.

Spoke are configured in stub mode, the correct answer is A.

A is correct. I've done a lab with GNS3 and it works confirming the answer A

Mardouk is right. EIGRP Stub Routers cannot be used as a backup path between two hub sites. Chapter 3 - EIGRP Stub Routers

A is correct. Once the link between R1 and R2 is lost, R2 will send out EIGRP queries ONLY to neighbors that do not advertise a STUB flag. R3 and R4 are both advertising the Stub flags, therefore R2 never queries R3 or R4 for a route to R1. R2 looses the route to R1 - Answer is Def A

The correct answer is A • The EIGRP stub routing feature will prevent the remote device from advertising core routes back to the distribution devices. Routes learned by the remote device from Distribution 1 will not be advertised to Distribution 2. Therefore, Distribution 2 will not use the remote device as a transit for traffic destined to the network core https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15-mt/ire-15-mt-book/ire-eigrp-stub-rtg.html

I agree. Stub areas cannot be transit areas

Mardouk is right