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How To: Setup Global Server Load Balancing (Part 1 of 2)

In this AskSupport How To video you will learn how to Setup Global Server Load Balancing (Part 1 of 2)

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Transcript : Hi, I’m Ronan O’Brien from the EMEA Citrix Tech Support Readiness Team, and today we’re going to take a look at the GSLB configuration. We’ll first take a look at the GSLB process flow. We’ll talk about how it works. And then I’ll step in and configure it for you in the lab and demonstrate the functionality. So, first of all, GSLB. What is it? Okay. It stands for Global Server Load Balancing. The example I’m going to be configuring for you today, we’re going to use a, we call it DNS Proxy Configuration. So, in effect, it is a DNS based global server load balancing solution. We can see that we need at least two appliances to configure this. Okay? These are not in a HA pair, that’s the one thing to bear in mind. They may have a secondary box at their own site, but they are not paired with each other. Okay? Now, what’s the theory? Okay? The client or the end user, here at their laptop they would type in, for example, a DNS name into their web browser. So we’re going to call that the fully qualified domain name, or FQDN for short. The browser needs to resolve that. Okay? Because it doesn’t know what IP that’s supposed to go to. So it says to its local DNS server, “Hey, what’s the IP address for this DNS name?” The DNS server wouldn’t have it in its local cache, doesn’t know, so it says, “Okay, well I don’t know what the IP is, but I’m going to ask the root server where to find the IP.” Right? So the IP address is configured, or is being served, from this DNS server here. Right down on the bottom. This is sitting behind the NetScaler infrastructure. Now, this DNS record can also be configured here on the NetScaler appliance. The way I’ll set it up in the lab, just to demonstrate it easier, we’re going to have this DNS server behind the appliance. So the DNS request eventually, the IP lookup request, eventually terminates on the appliance. Okay? It has a DNS V server, and it’s normally passing all these DNS requests to the backend DNS server. Now, because it’s doing GSLB for that particular FQDN, it doesn’t send the request to the backend. Instead, it answers it. Okay? It will reply with an IP address. Which IP does it use? It uses an IP, the size on the IP, by its logic, so it talks…it’s talking all the time with metric exchange protocol to it’s partner here. And it will then decide on an IP based on the logic. Okay. It can use roundtrip time to discover which machine has the fastest path back to the client. It can use round robin. We can use proximity base load balancing, which site is nearer to the client. Okay? We’ve a whole bunch of different methods that we can use for choosing whichever site we want to send the person to. So we have basically a V server here, our basic V servers, and then we have our content. So, in this particular example, we can see here the blue traffic is DNS. The IP eventually filters back to the client. It just so happens that the correct…or the…it decides to send the client to this part…to this particular site here. So it responds with an IP address that exists on the…that can exist on the appliance, and that’s what the client then connects to. Okay? It stores it in its local cache, the local DNS server. So further requests will go there and just have a customizable time to live. Right? So that’s basically how DNS…how a DNS based GSLB works. Okay? It’s quite simple, but it does rely on the DNS infrastructure. If someone types in an IP address from the get-go, we’re not going to use GSLB. So, let’s take a look at the configuration. I’ve got two NetScaler appliances here. And we’re going to use a simple web server here. Right? So I’ve got one green and one red. Right? The content would normally be the same on the backend. Right? So you normally wouldn’t have different content at each different site. If you’re providing…if you want to do sort of redundancy, so that if one site did have a problem with its Internet connection, for example, then you’d want that to be as transparent as possible to the end user. The end user shouldn’t know that they’ve changed to a different site. They might lose some session data, of course, but, you know. So let’s type in the IP addresses here. We just have a look. This is one. We have our green web server. And we have our red. All right? So each one of these is basically a V server running on the appliances. Now, you’ll notice that I also have a DNS V server configured here. This is just so I can use…obviously we can’t use a browser to look at a DNS V server, but I’m just going to use ns lookup. Okay? And now I just choose…type the command server, and I’m going to tell it to use this to send all further DNS requests to. So, if I type in google.com, I get the answers back. So what’s happened here is, this request has been sent to this DNS V server. It’s passed it back to a service, okay, backend service here, and it then gives me the response back. Okay? I have the same configuration done on this other NetScaler here. Okay, so we’ll be using this method to demonstrate the functionality of the GSLB. Now, let’s configure it. So we go to the GSLB section down here. And the first thing we need to do is, we need to add a site. Okay? So I’ll click Add and type this…it’s going to be a Local…LocalSite. Then we have to give it an IP address. Okay? So this is how the appliances talk to each other. 54 is what I’ll choose. And then you leave everything else blank. Okay? We just want to keep this as simple as possible, okay? So there are impacts of turning these on and off. We have parent site, we can have parent and child GSLB sites, but let’s just keep it simple: two small ones for the moment, just to demonstrate how it works. So we create this one, and I’ll create Red, which is like the remote site. 148. Create. Okay. Now, let’s go on to the other system, the GSLB. The sites. Click Add. 48. And then I’m going to create in GreenSite. 54. So you see what I’ve done has created a site in each of those boxes. Now. Okay.