# Can external devices like F5 BIG-IP use MTLs certificates to talk to mTLS meshed pods? **URL:** \ **Category:** Linkerd General Discussion\ **Tags:** mtls, certificates\ **Created:** [November 14, 2025, 9:44am UTC](https://linkerd.buoyant.io/t/can-external-devices-like-f5-big-ip-use-mtls-certificates-to-talk-to-mtls-meshed-pods/826 "2025-11-14T09:44:27Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![Nikolayy1](https://avatars.discourse-cdn.com/v4/letter/n/dfb087/32.png) [@Nikolayy1](https://linkerd.buoyant.io/u/Nikolayy1)\ **Post date:** [November 17, 2025, 9:41pm UTC](https://linkerd.buoyant.io/t/can-external-devices-like-f5-big-ip-use-mtls-certificates-to-talk-to-mtls-meshed-pods/826/2 "2025-11-17T21:41:06Z")
After a lot of and I mean a lot of investigation I think linkerd can’t mesh with external systems even if it is not mentioned because: - Require the TLS/HTTP2 ALPN custom extension `transport.l5d.io` - Uses not standard client/server certificates that are ECDSA with size 256 as they are changed very often and the secret for generating the certs is in thelinkerd namespace that tools like cert-manager can create the secret ([Automatically Rotating Control Plane TLS Credentials | Linkerd](https://linkerd.io/2-edge/tasks/automatically-rotating-control-plane-tls-credentials/) and the issue I discovered [Linkerd does not start when using Cert Manager and Trust manager to rotate the MTLS certs — Linkerd General Discussion — Linkerd Support Forum by Buoyant](https://linkerd.buoyant.io/t/linkerd-does-not-start-when-using-cert-manager-and-trust-manager-to-rotate-the-mtls-certs/825) ) but this secret can’t be used in another cluserissuer to create other secrets that will have the certs for other external systems. - Linkerd uses port **4143 for mTLS meshed traffic and the proxy internally knows to send it to the real backend app port.** --- _[View the full topic](https://linkerd.buoyant.io/t/can-external-devices-like-f5-big-ip-use-mtls-certificates-to-talk-to-mtls-meshed-pods/826)._