I am updating Practice Exam 2 (In Progress) for the CCIE Written Exam Bootcamp in your Members’s Site. I will be adding questions over the next couple of weeks. Currently, you will find some new Multicast Addressing/IGMP/MLD questions in there for your entertainment.
I am focusing on Practice Exam 2 right now for two main reasons. 1) It is allowing me to address some deficiencies with Practice Exam 1 and the lectures, and 2) More and more students are using this bootcamp as a prep tool for the dreaded Core Knowledge section.
Let us examine one of the new questions and walk through my solution logic.
Q. How does a router respond after receiving an IGMP Leave Group message?
a. The router does nothing
b. The router responds with a Membership Report
c. The router responds with a Group Specific Query
d. The router responds with a General Query
Hmmm, OK, I do not remember this right off, but let me see if I can reason through the answer. The IGMP Leave Group message, yes…this excellent IGMP Version 2 invention was designed to help with “Leave Latency” in Multicast. This is the issue where a receiver silently goes away and the poor router does not know this and keeps sending multicast frames out an interface for no reason whatsoever.
So, let me see what makes the best sense here. Would the router do nothing (option a)? No, that does not seem like a good use of technology.
Does the router respond with a Membership Report? Hmmm, I think it is the hosts that use Membership Reports to signal their participation in the multicast group.
Does the router respond with a Group Specific Query? Now that seems to make a lot of sense. Query the segment’s specific multicast group to see if there is anyone left in the segment that wants the multicast feed. I really like this response, but let me check the final option….
Does the router respond with a General Query? Well, this might work, but it seems like option C makes a lot more sense for the whole IGMP process.
I am going with Option C as my final answer! Too bad I cannot phone a friend (Petr Lapukhov)…
Enjoy the new questions everyone!
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