open-consul/website/content/docs/connect/proxies/index.mdx

---
layout: docs
page_title: Service Mesh Proxy Overview
description: >-
  In Consul service mesh, each service has a sidecar proxy that secures connections with other services in the mesh without modifying the underlying application code. You can use the built-in proxy, Envoy, or a custom proxy to handle communication and verify TLS connections.
---

# Service Mesh Proxy Overview

Proxies enable unmodified applications to connect to other services in the service mesh. A
per-service proxy sidecar transparently handles inbound and outbound service
connections, automatically wrapping and verifying TLS connections. Consul
ships with a built-in L4 proxy and has first class support for Envoy. You
can plug other proxies into your environment as well. This section describes how to
configure Envoy or the built-in proxy using Connect, and how to integrate the
proxy of your choice.

To ensure that services only allow external connections established through
the service mesh protocol, you should configure all services to only accept connections on a loopback address.

## Dynamic upstreams require native integration

Service mesh proxies do not support dynamic upstreams.

If an application requires dynamic dependencies that are only available
at runtime, you must [natively integrate](/consul/docs/connect/native)
the application with Consul service mesh. After natively integrating, the HTTP API or
[DNS interface](/consul/docs/services/discovery/dns-static-lookups#service-mesh-enabled-service-lookups)
can be used.