BROCADE IP PRIMER

Session PersistenceNow, let's say that we want the specific host 1.2.3.4 to always be directed toGroup 1 (rs1) when it connects to our virtual server. But, we want any hostscoming from the 123.2.1.0/24 network to be directed to the image servers inGroup 3 (image1 and image2). Any other source IP should be directed toGroup 2 (rs1, rs2, and rs3). Now define the policy:SLB-ServerIron#conf tSLB-ServerIron(config)#server pbslb add 1.2.3.4 1SLB-ServerIron(config)#server pbslb add 123.2.1.0/24 3SLB-ServerIron(config)#server pbslb default-group-id 2The policy states that all traffic from coming from 1.2.3.4 will be directed toreal server Group 1. All traffic coming from the network 123.2.1.0/24 will bedirected to real server Group 3, and any other traffic (the defined “defaultgroup-id“)will be directed to real server Group 2. That's what we want. Now,how do we enable it?SLB-ServerIron#conf tSLB-ServerIron(config)#server virtual-name www 1.1.1.3SLB-ServerIron(config-vs-www)#port httpSLB-ServerIron(config-vs-www)#port http sw-l4-pbslbSLB-ServerIron(config-vs-www)#bind http rs1 httpSLB-ServerIron(config-vs-www)#bind http rs2 httpSLB-ServerIron(config-vs-www)#bind http rs3 httpSLB-ServerIron(config-vs-www)#bind http image1 httpSLB-ServerIron(config-vs-www)#bind http image2 httpNotice that we've bound all five real servers to the virtual servers. You wouldthink this means that load balancing would take place on all five servers. If itweren't for the “sw-l4-pbslb,” that would be the case. However, because of thatline, the servers will be load balanced to according to our defined policy.Session PersistenceThe Worldwide Web has become more and more a part of everyone's daily life.As a result, businesses and other organizations understand how important it isto make sure their Web sites are always up. One of the more conventionalways to do this is to use a farm of servers to support the Web site. If one serverexperiences difficulty, the site is still available to the user. ServerIrons are amajor part of this type of infrastructure.But what if we have a specific web application or function? What if a client'stransaction starts on one server, but then gets load balanced to a differentserver? The new server doesn't have any information about the transaction itspredecessor just started. The problem I'm describing is referred to as SessionPersistence, and it continues to be one of the foremost struggles of webdesigners and infrastructure engineers. We need the redundancy of multipleservers, but we also need certain functions to be performed on a persistentmachine (once initiated).The Brocade ServerIron provides several methods to combat this problem.We'll cover a few of them in this chapter.Brocade IP Primer 357