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300-410 Exam - Question 257

Refer to the exhibit. The network administrator configured the Chicago router to mutually redistribute the LA and NewYork routes with OSPF routes to be summarized as a single route in EIGRP using the longest summary mask: router eigrp 100 redistribute ospf 1 metric 10 10 10 10 10 router ospf 1 redistribute eigrp 100 subnets

!

interface E 0/0

ip summary-address eigrp 100 172.16.0.0 255.255.0.0

After the configuration, the New York router receives all the specific LA routes but the summary route. Which set of configurations resolves the issue on the

Chicago router?

Show Answer
Correct Answer: B

The correct configuration to resolve the issue on the Chicago router involves using the interface parameter command to summarize the specific LA routes. In this case, the correct summary address is 172.16.8.0 with a subnet mask of 255.255.252.0, which will encompass the LA routes 172.16.8.0/24, 172.16.9.0/24, 172.16.10.0/24, and 172.16.11.0/24. This makes the longest summary mask in the context of EIGRP summarization. Thus, the configuration that should be applied is: interface E 0/1 ip summary-address eigrp 100 172.16.8.0 255.255.252.0.

Discussion

6 comments
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ChillingAgainOption: B
Nov 4, 2022

Answer is B. Summarized route for 172.16.8.0/24, 172.16.9.0/24, 172.16.10.0/24, 172.16.11.0/24 is 172.16.8.0/22. Which is noted as 172.16.8.0 255.255.252.0

inteldarvidOption: B
Jul 16, 2023

B correct: The advertisement of summary routes occurs on an interface-by-interface basis. For classic EIGRP configuration mode, you use the interface parameter command ip summary-address eigrp as-number network subnet-mask [leak-map route-map-name] to place an EIGRP summary aggregate on an interface.

PietjeplukgelukOption: B
Jan 11, 2024

Did not see any references, but the original question states "interface E 0/0" summary need to be created in EIGRP AS that only is activated at "interface E0/1". Also the subnet mask of /16 is to generic, and can be summarized more to specific /22: "172.16.8.0 255.255.252.0"

RemsyncOption: D
Oct 28, 2022

D is the correct answer. Even though both B and D solve the problem, the question is asking for the longest summary mask. D is summarizing with a /16 while B is doing it with a /22. /16 is longer than a /22. Answer D.

ChillingAgain
Nov 4, 2022

Longer prefix means more subnet bits. So /22 is longer than /16. So answer is B

diskman
Apr 16, 2024

Completely inverse as you said, the longer mask means the higher numbers after slash "/" composed of longer length of bits "1" within four octets comprising the mask.

diskmanOption: B
Apr 16, 2024

Option B looks closed to be the answer but should be with the network 172.16.4.0 255.255.252.0 (172.16.4.0/22) to summarize the routes generated from New York site.

9410480
May 11, 2024

I believe 172.16.8.0 is correct, because the question states "New York router receives all the specific LA routes but the summary route", so we are trying to summarize the New York routes, not the LA routes.

9410480
May 11, 2024

I mean the LA routes, not the New York routes. My bad!

SeMo0o0o0Option: B
Jul 21, 2024

B is corerct