In the v2 API, we allow multiple TlsCertificates to be specified per DownstreamTlsContext (https://github.com/lyft/envoy-api/blob/master/api/tls_context.proto#L107). In the current Envoy implementation, each TLS context only supports a single certificate/key (https://github.com/lyft/envoy/blob/master/source/common/ssl/context_impl.cc#L77). This issue will track the design and implementation of multiple cert support. @PiotrSikora