BROCADE IP PRIMER

Chapter 15: Server Load Balancing (SLB)That's all you need to add. Now, when the virtual server “www” hands off to rs1or rs2, it will use DSR. The health checks on rs1 and rs2 will know that DSR isbeing used as well. If the loopback does not exist on these real servers, theywill fail the health check.Does this mean that you could have one virtual server port (say, http) usingDSR, and a different virtual server port (say, smtp) on the same virtual serverthat is not using DSR? Yes, that's what this means. DSR is unique to the virtualserver port.Configuring Multiple VIPs to the Same RealServerThere are times when you may want to bind the same real server port to differentvirtual servers. Let's say we have our virtual servers “www” and “mail”, butwe want to create a new virtual server called “images”:SLB-ServerIron#conf tSLB-ServerIron(config)#server virtual-name images 1.2.3.50SLB-ServerIron(config-vs-www)#port httpSLB-ServerIron(config-vs-www)#predictor least-connSLB-ServerIron(config-vs-www)#bind http rs1 httpThis port is already bound to another virtual server.SLB-ServerIron(config-vs-www)#What happened? Oh, that's right. We've already bound HTTP on rs1 with virtualserver “www.” What can we do? We need to use rs1. Can't it be bound to both?Yes, but it requires an additional port: a shadow port. This is a fake port thatwe will add to the real server sub-config. Its sole purpose is to allow us to bindthe same real server to different virtual servers on the same port. Whenchoosing a shadow port, it's wise to pick a number that you know you aren'tgoing to use later. For example:SLB-ServerIron#conf tSLB-ServerIron(config)#server real rs1SLB-ServerIron(config-rs-rs1)#port 12345Now wait a minute! Isn't the ServerIron going to try a Layer 4 health checkgoing to TCP or UDP port 12345? Think back. What determines the Layer 4health check? This only happens when a real server port is bound, right? Let'stake a look at that process. Let's go back to “images”:SLB-ServerIron#conf tSLB-ServerIron(config)#server virtual imagesSLB-ServerIron(config-vs-www)#port httpSLB-ServerIron(config-vs-www)#no port http translateSLB-ServerIron(config-vs-www)#bind http rs1 12345344 Brocade IP Primer