350-001 Question #175: Real Exam Question with Answer & Explanation

The correct answer is C: Gi3/7. IP 225.230.57.199 will become MAC 0100.5ee6.39c7, so the interfaces G3/7, F6/28 and F7/20 will receive the traffic. Mac address 0100.5e66.39c7 is accessible via Gi3/4, Gi3/7, Fa4/10, Fa4/14, Fa7/31, and Fa7/40. So options C and E i.e., Gi3/7 & Fa4/14 are the correct answers. Firs

Question

Refer to the exhibit. From the MAC addresses shown in the command output, to which two ports is the multicast stream 225.230.57.199 being forwarded on this switch? (Choose two.)

Exhibit

Options

AFa6/28
BFa7/20
CGi3/7
DFa4/2
EFa4/14
FFa4/38
GFa6/28
HFa5/7

Explanation

IP 225.230.57.199 will become MAC 0100.5ee6.39c7, so the interfaces G3/7, F6/28 and F7/20 will receive the traffic. Mac address 0100.5e66.39c7 is accessible via Gi3/4, Gi3/7, Fa4/10, Fa4/14, Fa7/31, and Fa7/40. So options C and E i.e., Gi3/7 & Fa4/14 are the correct answers. First thing is to convert the IP address to binary so: 225.230.57.199 in binary is 11100001 11100110 00111001 11000111. Then put the first 6 hex characters in front of the binary address and remove the first 4 bits (which are always 1110) this is the IEEE OUI for layer 2 multicast addressing 0100.5e | 0001 11100110 00111001 11000111. Then we "always" change the next 5 bits to a binary 0 (which leaves us with 24 bits for the conversion to hex) 0100.5e | 01100110 00111001 11000111 This leaves you with 24 bits to convert into hex from binary. Thus 01100110 00111001 11000111 = 66.39.c7 and the question asks which interfaces listed are forwarding this group... All of the following interfaces below are forwarding this: Gi3/4, Gi3/7, Fa4/10, Fa4/14, Fa7/31, Fa7/40 But only 2 are listed in the multiple choice:

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