Refer to the exhibit.
Why is the neighbor relationship between R2 and R4 shown as ES-IS?
A.
because there is an MTU mismatch between R2 and R4
B.
because interface S3/0 of R4 is configured as L1/L2
C.
because interface S3/0 of R2 is configured as L1
D.
because there is a hello interval mismatch between R2 and R4
Explanation:
We see ES-IS when either one side is configured to send only L2 and another side is configure to
send L1. In this case both sides show each-other as ES-IS. However, from the diagram we see that
one side is sending L1 and L2. We also can see ES-IS when we have MTU Mismatch
The answer is C.
Please check this pdf, page 27:
https://www.google.co.il/url?sa=t&source=web&rct=j&url=http://monsterdark.com/wp-content/uploads/BRKRST-2327.pdf&ved=0CCIQFjAEahUKEwiX8qPQt7rIAhWMWhQKHVULDiE&usg=AFQjCNE0yFeV4FBP4VwMVKj5gs5DYJlR5w&sig2=zw2ossVzq66QPmO9tBY7WA
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Agreed. The answer is C.
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A is the correct answer
http://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/47201-isis-mtu.html
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A is a cisco preferred answer
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A and C are correct but A is only correct if the default state of IS-IS is changed so that it no long pads MTU’s. In this question they specifically SHOW that the IS-IS circuits are mismatched while they do NOT say anything at all about changing the default actions of IS-IS. I would have to say they are probably testing your knowledge of IS-IS interface circuit configuration here.
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C correct 100%. Tested this case on GNS3.
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Look at the R1 neighborhood. It says “L1” and not “L1L2”. It means the “L1” description on the picture is not about the circuit, but about the IS-type. I have made the test with such a configuration and got the “show” output above. No MTU change was necessary. I have changed MTU later and there was no change in the “show” output. My next test was to bring back “L1L2” config on R2 leaving the mismatching MTU. The “L2” neighborhood between R2 and R4 reappeared. Changing isis hello interval has no influence.
So my option is “C”.
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