I have a public web server that's also extensively used from the LAN. We're standing up a Windows AD CA server for the LAN side but we'll also need a public SSL Certificate for the web server. The website url resolves to the interal ip on the LAN so I'm assuming I'll need to have both a public certificate and a lan certificate installed at the same time.

How can this be accomplished?


You can use single public certificate for both, external and internal clients. There is no need to use separate certificate for internal clients. Keep things simple.

  • So the certificate is by domain and does not contain the IP? – Robofan Jun 13 at 19:23
  • yes, all clients connect to server by a public name specified in the certificate. – Crypt32 Jun 13 at 19:25

You can't use different certificates for the same website (*). Use a public certificate, internal clients will trust it just fine.

(*) There are workarounds, but they are quite cumberstome and you shouldn't use them unless absolutely required.

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    Technically you can. You can bind a different certificate for each IP and With SNI you can use different certificate for each domain on the same IP. – yeya Jun 13 at 21:01
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    @yeya As I was saying, there are workarounds :) You can have multiple websites hosting the same content on different IPs with different certificates, or you can use a reverse proxy to externally publish with a public certificate an internal web site which uses a private one. But my point was, unless you actually need different certificates for internal and external users, this is complex and useless. – Massimo Jun 13 at 21:39
  • @Massimo, I may have to set up a L4 proxy at some point in the future to support differing content policies. If that becomes the case, would it just be a matter of using some command in a server block in nginx to choose which cert to serve? – Robofan Jun 14 at 3:23
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    @Massimo: What defines whether e.g. TLS SNI is a "workaround" rather than full "ability"? – grawity Jun 14 at 6:46
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    @Robofan with a reverse proxy (not a forward one) you can expose a web site to the Internet using SSL termination, thus you can accept external connections on the reverse proxy using a public certificate, and then have the proxy connect to the internal web site which instead uses a private certificate. But if you are actually using a public certificate on the web site itself, you don't need such further complications. – Massimo Jun 14 at 8:38

I would agree with the other comments that if a simpler setup works for you, go simple. But to answer your original question, you can have multiple site bindings - you would setup one with the internal IP address and internal certificate, and another with the external/DMZ IP and public certificate. I would also suggest defining a host name per binding and selecting the Require SNI checkbox (not checked below but should be).

IIS Site Bindings, https selected

  • While technically correct, your answer assumes that the server has two IP addresses, one internal and one external/DMZ; this is quite unusual for a web server. – Massimo Jun 14 at 16:06
  • You’re right (though a public web server with a LAN-exposed direct route isn’t great practice), and now I read your comments and see you’ve already thoroughly discussed this. I don’t think I’ve added anything that hasn’t been said yet. – mlhDev Jun 15 at 1:45

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