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.)
Switch#show mac-address-table multicast
A.
Fa6/28
B.
Fa7/20
C.
Gi3/7
D.
Fa4/2
E.
Fa4/14
F.
Fa4/38
G.
Fa6/28
H.
Fa5/7
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:
Gi3/7 & Fa4/14