Multicast Explained in 5 Minutes | CCIE Journey for Week 6-12-2020

another week on my CCIE journey is in the books what have I been up to and can I explain multicast in five minutes let's find out I didn't record a video last week and that's okay I had a sick child it's very important to put family first and when he's sick that's what really matters to me I don't want to spend my time studying and recording when I need to be taking care of my family but that doesn't mean I didn't make progress I've made a lot of progress at this point I'm actually about halfway through with the encore textbook and of course I'm watching CBT Nuggets to supplement that my method has always been watched the Nuggets first just so I get the high level great explanation and understanding dig into the details with the textbook and then finish with practice exams before taking the exam so I've already watched these Nuggets before I get access to watching them before they're even released so I'm watching them again while I'm reading the relevant topic and this week I focused heavily on multicast QoS and the IP services so that's things like NTP the first hop redundancy protocols and then NAT so that's been what I've been focusing on this week last week in since I didn't bring this up I did finish up pretty much all of the IP routing items that I was worried about there that would be eigrp OSPF and of course bgp which are things that i've already been pretty comfortable with in the past but it doesn't hurt to dig into them lab them up even some more so this week somebody tweeted me and said they would love for me to try to explain multicast and what I'm gonna try and do is I'm just gonna give a high-level summary I'm gonna try and get it done in under five minutes this always helps me to talk about these topics that I'm learning about too and while I've done multicast in the past this is really pushing me beyond my comfort zone so without further ado let's jump on the whiteboard see if I can explain multicast in five minutes so multicast solves the problem of one device like this server here trying to initiate sessions to multiple endpoints what we call receivers which are going to be these green squares that are supposed to represent computers but I'm terrible at drawing so in a unicast setting all of these devices could form sessions directly to this server and get the streaming information that way but that would obviously clog a bandwidth all of these routers along the way and the server itself would have to maintain sessions for each one of these devices and here we've only got five devices on the screen but what if we had thousands or even tens of well that would obviously be unmanageable a broadcast is also a way that we could handle these situations but now every single device on the network has to manage that packet whether it wants the data or not multicast solved this problem by the server sending in one stream of data into the network and then the devices choosing to subscribe to that stream if they want to multicast packets have to be routed just like a router has to route unicast packets but it does all of this subscription and routing through a couple different protocols the first protocol that comes into play here is called IGMP and this occurs at layer two IGMP is basically started by the endpoint here the receiver who tells the router hey I want to subscribe to a stream that's on a multicast IP something like 224 one two three so the endpoint the computer here the receiver says I want to subscribe to 224 dot one to two to three please mister router go find that for me there's a lot more that goes into IGMP but that's the gist of it IGMP just occurs between the router and the endpoint these receiver here from there pim steps into play and that occurs at layer 3 there are a bunch of different flavors and deployment methods or modes for pim but the idea here is that this router at this point is now trying to find the most efficient path to get to the server so when all the interfaces on this router that pim is running it will start sending messages out to the next router saying hey if you see a stream for 220 4.1.2 dot three I want it now how it arrives to this conclusion that depends on the flavor of pim that you're deploying there could be things called like a rendezvous point where all the routers check in first before receiving the stream or these streams check in with that first before sending it on to a client the rendezvous point is basically like the friend who's hooking you up with a blind date hay receiver meet the server server mate the receiver and then from there they go on the date and they figure out their own path forward and once they figured out the own path forward at least in Cisco deployments the router were then build the fastest path or the shortest path to the end point to make the most efficient way to collect the stream from the server and get it into the hands of the end points but how the router gets it into the hands of the end points is where it gets pretty interesting let's clear the screen and talk about what happens in this link right here think about the goal of multicast again for a moment multicast stream has made its way into the router and now it's time to get it into the hands of our green receiver here the orange receiver doesn't want that stream it's not subscribed to it how does it work the point of multicast was to simply send a stream out towards a group of clients and if the group of clients want that stream they can access it so by default what this router is going to do is it's going to send that stream into the segment which hits this switch and the switch by default is going to send it to all of the receivers on that segment so even the orange client that doesn't want that multicast stream is going to get it and it's gonna have to end up discarding what's really happening under the hood here is we have the multicast IP address the multicast group here to 24.1 2.3 that's all great and all because that's layer 3 but now at this point we're on layer 2 so layer 2 technologies are what's gonna have to carry the stream from the router into the endpoint so what happens under the hood is a multicast MAC address 0 1 0 0 5e and then the remaining 3 portions are gonna be built using the multicast IP address so just for simplicity sakes this isn't correct I'm going to put this 1 2 3 so the destination frame will be this MAC address the router sends that destined to that MAC address into the switch and here's the kicker because no device has that MAC address as their source that MAC address does not exist in the MAC address table on this switch and what does a switches default behavior when it receives a frame that it doesn't know the destination to it sends it out every port in the same V link so when the green client says I want that stream it does begin listening on that MAC address but again it will never source a frame with that MAC address so the switch will never learn about that mac-address from that poor again because the default behavior is going to be descended out all ports on that segment it's gonna get sent out towards the orange client here too and because the orange client isn't listening on that MAC address it will be dropped at the Nick that still creates a lot of unnecessary choke in this segment right here so what the switch kit enable is something called igmp snooping that way when the green client sends in its IGMP join request basically saying hey mr. router I want to listen to this group the switch can then associate the destination MAC address with that port and it will only ever be sent out the correct port again so that's been the crash course of multicast obviously multicast is a lot more complicated than that when you start talking about the different PIM modes like dense mode sparse mode source-specific multicast and one of the cool things about multicast and specifically on core training is that Keith Parker didn't explain it in five minutes he goes into detail and even demos how to configure in-lab multicast within the virtual labs in the CBT Nuggets encore course it's been crucial for my multicast training watching his content on CBT Nuggets so if you haven't checked out the encore content on CBT Nuggets or if you're interested in multicast I can't stress it enough check out the description for my link to the Encore content and you'll get fired up ready to go learning for encore training so how am I feeling overall about my journey towards CCIE and getting towards encore at this point and halfway through the book I'm doing good following along with CBT Nuggets but it is a tremendous amount of content I'm starting to get that overwhelmed feeling like maybe end of June or early July is a bit aggressive I need to take my time a little bit slower and master this content even more I really want to nail this exam I don't need to crush it but I want to pass it for sure I want to pass it on my first try so it really comes down to how I'm performing on the practice exams I am going to be using the boson practice exams and I will demo those practice exams here on my channel when that time comes so look at that for the end of June but until then that's been the progress towards my CCIE journey tackling multicast QoS and was I services this week thanks for stopping by I'll see you in the next one

Channel: Data Knox

Views: 30,004

Rating: 4.875 out of 5

Keywords: ccie routing and switching, ccie certification, cisco ccie, ccie enterprise, ccie journey, my ccie journey, data knox ccie, data knox cisco, cbt nuggets ccie, cisco certifications, network engineering, cisco training, cisco certification, ccie study, ccie lab, ccie collaboration, cisco ccna, encor ccie cisco, cisco ccie lab, multicast routing, multicast tutorial, multicast routing explained

Id: W5oMvrMRM3Q

Length: 9min 14sec (554 seconds)

Published: Fri Jun 12 2020