<p>Replaces the set of policies associated with the specified port on which the EC2 instance is listening with a new set of policies. At this time, only the back-end server authentication policy type can be applied to the instance ports; this policy type is composed of multiple public key policies.</p> <p>Each time you use <code>SetLoadBalancerPoliciesForBackendServer</code> to enable the policies, use the <code>PolicyNames</code> parameter to list the policies that you want to enable.</p> <p>You can use <a>DescribeLoadBalancers</a> or <a>DescribeLoadBalancerPolicies</a> to verify that the policy is associated with the EC2 instance.</p> <p>For more information about enabling back-end instance authentication, see <a href="https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-create-https-ssl-load-balancer.html#configure_backendauth_clt">Configure Back-end Instance Authentication</a> in the <i>Classic Load Balancers Guide</i>. For more information about Proxy Protocol, see <a href="https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/enable-proxy-protocol.html">Configure Proxy Protocol Support</a> in the <i>Classic Load Balancers Guide</i>.</p>

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