Is it me or they never explained fully multicast addresses in the CCNA curriculum?

We know what they look like due to routing protocols using them. However, we also know that switches flood them when received. In that case, how is multicast better than broadcast?

I have heard from somewhere that broadcasts cause congestion not because they use lots of bandwidth, but because every host receiving them must process them. From that statement, I deduce that processing broadcasts which are not relevant to a specific host is much more laborious than processing multicasts which are not address addressed to that host. If that deduction is right, is that the only reason why multicast is better?

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Comments

jovan88

They went pretty into it in the old CCNP track, not anymore though. Basically when IGMP snooping is enabled it will prevent the multicast traffic being flooded out all ports.

Slowhand

There's a LOT that they don't go into fully on the CCNA exam(s). Quite frankly, that was one of the most frustrating things about studying for my CCNA, (640-801 in my case,) that so many things were left to "learn about later, when you're more advanced." In my case, I was frustrated over the fact that, while we learned a lot about setting up frame-relay connections from the end-point routers, nothing was mentioned in the CCNA study guides about what went on in the cloud; not even so much as a basic in-a-nutshell overview was given. I was also more than a little bit peeved that there was no practical training given on setting up a T1 circuit, seeing as how I was working for an ISP at the time and it would have been good stuff to learn in order to convince my boss to let me start doing more advanced things. So, I decided that going outside the CCNA curriculum was necessary in order for me to see the bigger picture.

What I ended up doing was studying ahead a little bit. While it may be a bit overkill for the cert, I bought myself a copy of Routing TCP/IP Volume I and Cisco LAN Switching, then read the chapters that corresponded to topics on the exam blueprint. For your purposes, poking around a bit on Cisco's site to read the more advanced articles on multicasting, along with something like Network Warrior, is probably going to do just fine. (Unless you don't mind a bit of overkill, then go nuts and buy a more advanced book.

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bermovick

I noticed that too! I used the 2-exam route, but I found in order to understand some of the materials, I needed to know more than what was given in order for it to logically make sense.

shaqazoolu

bermovick wrote: »

I noticed that too! I used the 2-exam route, but I found in order to understand some of the materials, I needed to know more than what was given in order for it to logically make sense.

I found that that Self-Study guide for ICND2 from Cisco Press actually touched on a lot of that stuff and noted that it was just to help with the concept and not necessary for the exam. Someone told me that multicast stuff is broken down a lot more in the CCNP material.

pitviper

shaqazoolu wrote: »

Someone told me that multicast stuff is broken down a lot more in the CCNP material.

Not any longer – It’s apparently been omitted from the latest CCNP track. I started reading up on it on the side since it’s touched on in the CCVP but not in nearly enough detail.