Exam 300-101 topic 2 question 558 discussion

Actual exam question from Cisco's 300-101

Question #: 558
Topic #: 2

Refer to the exhibit.

A Boston company bought the assets of a New York company and is trying to route traffic between the two data networks using EIGRP over EoMPLS. As a network consultant, you were asked to verify the interoperability of the two networks.
From the show ip route command output, what can you tell the customer about the traffic flow between the subnet in New York (172.16.8.0/24) and the subnets in
Boston (172.16.16.0/24 and 10.10.16.0/24)?

A. Traffic is flowing between the 172.16.8.0 subnet and subnets 172.16.16.0 and 10.10.16.0 and no configuration changes are needed.
B. Auto-summary must be disabled on N1 and B1 before traffic can flow between the 172.16.8.0 subnet and subnets 172.16.16.0 and 10.10.16.0.
C. Traffic will flow between the 172.16.8.0 subnet and 172.16.16.0 without any further configuration changes. However, auto-summary must be disabled on N1 and B1 before traffic can flow between the 172.16.8.0 subnet and the 10.10.16.0 subnet.
D. Auto-summary must be disabled on N1 and B1 before traffic can flow between the 172.16.8.0 subnet and the 172.16.16.0 subnet. However, traffic will flow

Show Suggested Answer

Suggested Answer: between the 172.16.8.0 subnet and 10.10.16.0 without any further configuration changes. 🗳️
Basically auto route summarization happens at the classful network boundary...so that would make N1 and B1 the locations that summarization would occur for the 172.16.0.0/16 classful networks.
So if you left auto-summarization enabled on those 2 routers, you would have an issue with discontiguous networks being advertised by both routers N1 and B1 with their classful mask (172.16.0.0/16 and 10.0.0.0/8), which will cause you issues.
Turning off auto-summarization on N2 and B2 wouldn't make any difference, as their networks wouldn't be summarized due to the fact that they are not meeting a classful boundary on their perspective routers.

by Nemanja at Feb. 14, 2020, 8:07 p.m.

Comments

Submit Cancel

Nemanja

5 years, 4 months ago

B. Auto-summary must be disabled on N1 and B1 before traffic can flow between the 172.16.8.0 subnet and subnets 172.16.16.0 and 10.10.16.0.

upvoted 2 times

...