<p><span style="font-size:18px"><strong>What&#39;s the difference between external, internal, and classic ELBs?</strong></span></p> <p>The architecture of external type is LVS+Nginx, the architecture of the internal type is LVS host and backup mode, and the architecture of the classic type can satisfy the needs of the financial industry with underlying layer implemented with F5 devices.</p> <p>External ELB can provide external services, and the service address of the created instance is the public IP address.</p> <p>Internal and classic ELB can only provide services for the system inside the cloud platform, and the service address of the created instance is the internal IP address.</p> <p><strong><span style="font-size:18px">How can I use ELB products to publish websites?</span></strong></p> <p>You should purchase external ELB products. The service address of external ELB is public IP. Then, you need to deploy the Web business platform on the back-end server, and build the back-end server into a server resource pool. Binding the resource pool after creating the ELB listener can complete the website publishing on the Internet.</p> <p><strong><span style="font-size:16px">What protocols and algorithms does ELB support?</span></strong></p> <p>ELB supports four-layer TCP, UDP and seven-layer HTTP and HTTPS protocols.</p> <p>External and internal ELBs support the algorithms of RR (Round Robin) and WRR (Weighted Round Robin). Classic ELB supports the algorithms of RR (Round Robin), WRR (Weighted Round Robin) and WLC (Weighted Least Connections).</p> <p><strong><span style="font-size:18px">What session persistence modes does the listener support?</span></strong></p> <p>TCP and UDP listeners support the session persistence based on the source address Hash.</p> <p>HTTP and HTTPS listeners support session persistence based on the source address Hash and Cookies.</p> <p><strong><span style="font-size:18px">What&#39;s the difference between four-layer and seven-layer ELBs?</span></strong></p> <p>The four-layer (TCP, UDP) is based on connection to schedule traffic. TCP creates a socket access ELB instance, and the source IP, destination IP and port form a connection.</p> <p>The seven-layer (HTTP, HTTPS) is based on connection to schedule. For example, http gets requests to access a page.</p> <p><strong><span style="font-size:18px">Does internal ELB have redundancy mechanism to ensure the stability of business?</span></strong></p> <p>Yes, the internal ELB refers to two host and backup LVS virtual machines. It uses keep a lived mechanism to detect the active state between them. When the host LVS goes down, the backup LVS will detect and automatically switch to the host mode to take over ELB work. The switching time is 4.6 seconds.</p> <p><strong><span style="font-size:18px">Can internal ELB addresses be controlled by VPC security group?</span></strong></p> <p>Yes. You can use the security group function in VPC to configure your security group and add according to internal ELB.</p>