mediumMultiple Choice
CCNP Practice Question: Runs the following command on Router R8: R8# show…
A network engineer runs the following command on Router R8:
R8# show ip mroute count IP Multicast Statistics
Group: 239.4.4.4, Source: 10.0.0.9 Packets: 1500, Bytes: 1200000, Average rate: 8000 pps, 5 sec rate: 0 pps
Group: 239.5.5.5, Source: 10.0.0.10 Packets: 0, Bytes: 0, Average rate: 0 pps, 5 sec rate: 0 pps
Based on this output, what can be concluded?
⚠ Common exam trap
Cisco often tests the distinction between multicast route state (presence of an (S,G) entry) and actual traffic flow, so candidates may mistakenly assume that any entry in 'show ip mroute' implies active traffic, when in fact only non-zero packet/byte counters confirm forwarding.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Multicast traffic is flowing for group 239.4.4.4.
The output shows 1500 packets and 1,200,000 bytes received for group 239.4.4.4 from source 10.0.0.9, with an average rate of 8000 pps, indicating active multicast traffic. In contrast, group 239.5.5.5 shows zero packets and bytes, confirming no traffic is flowing for that group. The 'show ip mroute count' command displays per-group and per-source packet and byte counters, directly reflecting multicast forwarding activity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Multicast traffic is flowing for group 239.4.4.4.
Why this is correct
In the multicast routing table, the entry for group 239.4.4.4 shows non-zero packet and byte counters, which indicate that the router has actively forwarded or received multicast packets for this group. These counters increment as traffic traverses the (S,G) or (*,G) path, confirming live multicast flow. In contrast, the other group's entry remains at zero, so this is the only active group.
- ✗
Multicast traffic is flowing for group 239.5.5.5.
Why it's wrong here
The multicast table entry for 239.5.5.5 has zero packet and byte counters, which means the router has not received or forwarded any traffic for this group since the counters were last cleared. A zero count indicates either no interested receivers, no active source, or no traffic has matched the mroute entry. Therefore, the assertion that traffic is flowing for this group is unsupported by the show command output.
- ✗
Both groups are receiving traffic.
Why it's wrong here
The claim that both groups are active is contradicted by the counter values in the mroute table. Only group 239.4.4.4 shows incrementing packet and byte counts; group 239.5.5.5 shows zero counts, meaning it is idle. Since multicast traffic flow is directly indicated by non-zero counters, the statement 'both groups' is false because only one mroute has forwarded packets.
- ✗
The source for group 239.4.4.4 is 10.0.0.10.
Why it's wrong here
In the mroute output, the source address for the active group 239.4.4.4 is listed as 10.0.0.9, not 10.0.0.10. Confusing the last octet leads to the wrong answer; the correct source IP is explicitly shown in the routing entry's (S,G) pair. This is a common misreading of the source field in a multicast route.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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