<p>This article describes how to create a listener after creating an ELB instance. Listener is used to listen to the request sent to an ELB instance, and distribute the request to multiple back-end servers according to a predefined scheduling way.</p> <p>The following table shows the types of listener protocols supported by different types of ELB products and the function items that can be configured for listeners of different protocols.</p> <table border="1" cellpadding="0" cellspacing="0"> <tbody> <tr> <td style="background-color:#ededed; vertical-align:top; width:89px"> <p><strong>Instance type</strong></p> </td> <td style="background-color:#ededed; vertical-align:top; width:161px"> <p><strong>Listener protocol</strong></p> </td> <td style="background-color:#ededed; vertical-align:top; width:249px"> <p><strong>General configuration item</strong></p> </td> <td style="background-color:#ededed; vertical-align:top; width:277px"> <p><strong>Proprietary configuration item</strong></p> </td> </tr> <tr> <td rowspan="4" style="vertical-align:top; width:89px"> <p>Extranet</p> </td> <td style="vertical-align:top; width:161px"> <p>TCP</p> </td> <td rowspan="4" style="vertical-align:top; width:249px"> <p>Port, schedule algorithm, resource pool, session persistence, access control, health check</p> </td> <td style="vertical-align:top; width:277px"> <p>TCP+SSL certificate</p> </td> </tr> <tr> <td style="vertical-align:top; width:161px"> <p>UDP</p> </td> <td style="vertical-align:top; width:277px"> <p>Custom health check content configuration item</p> </td> </tr> <tr> <td style="vertical-align:top; width:161px"> <p>HTTPS</p> </td> <td style="vertical-align:top; width:277px"> <p>Certificate binding, Gzip data compression, and connection parameter configuration</p> </td> </tr> <tr> <td style="vertical-align:top; width:161px"> <p>HTTP</p> </td> <td style="vertical-align:top; width:277px"> <p>Gzip data compression and connection parameter configuration</p> </td> </tr> <tr> <td rowspan="2" style="vertical-align:top; width:89px"> <p>Intranet ELB</p> </td> <td style="vertical-align:top; width:161px"> <p>TCP</p> </td> <td rowspan="2" style="vertical-align:top; width:249px"> <p>Port, schedule algorithm, resource pool, and session persistence</p> </td> <td style="vertical-align:top; width:277px"> <p>Health check</p> </td> </tr> <tr> <td style="vertical-align:top; width:161px"> <p>UDP</p> </td> <td style="vertical-align:top; width:277px"> <p>&mdash;</p> </td> </tr> <tr> <td rowspan="3" style="vertical-align:top; width:89px"> <p>Classic ELB</p> </td> <td style="vertical-align:top; width:161px"> <p>TCP</p> </td> <td rowspan="3" style="vertical-align:top; width:249px"> <p>Port, resource pool, and session persistence</p> </td> <td style="vertical-align:top; width:277px"> <p>&mdash;</p> </td> </tr> <tr> <td style="vertical-align:top; width:161px"> <p>HTTP</p> </td> <td style="vertical-align:top; width:277px"> <p>&mdash;</p> </td> </tr> <tr> <td style="vertical-align:top; width:161px"> <p>HTTPS</p> </td> <td style="vertical-align:top; width:277px"> <p>Certificate binding</p> </td> </tr> </tbody> </table>