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So we're going to carry on with our discussion of Frame Relay with a discussion of various Frame Relay Topologies. Now there's two ways to provision a Frame Relay Network. You have Point-to-Point and you have Multipoint. We'll talk about Multipoint first because it is a little simpler to talk about. Multipoint has every WAN Interface on your network in the same Layer 3 Network. It's kind of like of having a big Ethernet Network on the WAN side of your network. The only downside is that you generally can't transmit Broadcasts across that hence this lab configuring Frame Relay or configuring EIGRP over MBNA networks. The advantage of Multipoint and really the only advantage of Multipoint Frame Relay is that it conserves IP addresses on your WAN Interfaces. If you think about it and you have a Point-to-Point Network for each one of your 500 locations, then that means you have to a little slash 30 network with two IP addresses in it for each one of your Point-to-Point Serial Links and you can chew through some IP addresses pretty quick if you have to do that and again, the advantage of Multipoint is that it's all on one big network and so you just have one big, you know, slash 20 network that has all of your WAN interfaces and they're all on one big network. It presents it's own interesting problems and again we'll see that when we go through the lab. Multipoint Networks usually use the single physical interface that is pointing at the WAN provider. You do all of your configurations on the physical interface instead of on Subinterfaces which again we'll get into here in a little bit. Now Point-to-Point Networks on the other hand are what you'll generally see in Production, even on very large networks. Now Point-to-Point Networks are generally, they're pretty much the opposite of Multipoint Networks. Each DLCI is it's own network, each DLCI has it's own slash 30 network. So you have an interface or a subinterface that actually has two IPs on it just like a Point-to-Point Serial Interface would. It more closely emulates a Non Frame Relay Network. It more closely emulates a network where you've got T1s going everywhere and again since that's kind of the background that preceded Frame Relay, that's kind of the way most engineers grew up, so to speak and they're going to be a lot more comfortable with that. Also where Multipoint Networks use a single physical interface, Point-to-Point Networks generally use subinterfaces for their Point-to-Point WAN Links and again when we'll see that when we go through the lab here in a little bit. So let's talk a little bit about Network Topologies. The first one we'll talk about is the Hub and Spoke Topology and this is kind of the topology we're going to be using on our lab. You'll notice that for each of our locations here we have a single logical network between each of them. We have one between Phoenix and Chicago and New Orleans and Atlanta. If one of these links go down then you have lost connectivity to that entire site. The second type of Network Topology we'll talk about is a Full-Mesh Topology and you'll notice that in a Full-Mesh Topology, every location can talk to every other location. Any one of these connections can go down, really any two or three of them can go down and you'll still have your full network. You know let's say that this link between Atlanta and Chicago goes down as well as this link between Phoenix and Chicago. Both of these go down for whatever reason, the Frame Relay provider has a failure in their network. You can still get traffic from Atlanta to Chicago by going through New Orleans. You can also get traffic from Chicago to Phoenix by going through either New Orleans or Atlanta depending on what links are faster in the Frame Relay Network here. This is a pretty expensive to do the network, generally because most Frame Relay providers charge you for each PVC that you have set up with them. However, if you have a big network where each in point might have to communicate with every other in point, for example this is a big MPLS Network and you have VOIP running over it. Well you don't want traffic from Atlanta to have to go through Phoenix and back to Chicago if you're just making a phone call between these two offices. So you'll pay for the connectivity between Atlanta and Chicago just so you can make your phone calls anywhere on your network that you want to go. And the last Network Topology we'll talk about a Partial-Mesh Network. Now you'll notice in this network we have full connectivity between Phoenix, Chicago and Atlanta and New Orleans, well they're off by themselves. You know, one of those guys had a New Orleans do anyway, there always at Mardi Gras or something like that and this is kind of the best of the both worlds. You know, let's say we have our big major offices in Phoenix, Atlanta and Chicago. Well we've got full connectivity there so you can make a call from Atlanta to Chicago and not have to go through Phoenix. However, New Orleans, you know, again, it's just a branch office with three people in it. You know, if this connectivity goes down, it's, it's a pain for New Orleans, but you know, we don't really want to have to pay for full connectivity from all these locations to New Orleans when there's only three people there and that's where the Partial-Mesh Network comes into play. And that's pretty much it. That concludes our overview and review of Frame Relay topics.
| Course: | Implementing Cisco IP Routing (642-902 ROUTE) |
| Author: | Greg Dickinson |
| SKU: | 34291 |
| ISBN: | 978-1-61866-028-2 |
| Release Date: | 2011-12-28 |
| Duration: | 10 hrs / 105 lessons |
| Work Files: |
Yes |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |