Doing a little searching I’ve found that a simple reverse proxy will not work for vcenter but i was able to find this repository which includes a sample nginx configuration and the other things needed to proxy vcenter.

I’ve got it working with vCenter 6 using ryanpq’s answer and some decent modifications.
this repository

Here’s my nginx.conf, minus my site’s name and some comments. I had to add some things and move things around, and I didn’t see that port 7331 was needed at all when I connected locally so it was removed. You can compare with what I’ve linked above. Keep in mind, ports 443 and 9443 need to be forwarded to your NGINX server. Also, remember that your vSphere web client will be at https://<vcenter ip>/vsphere-client. I hope this helps others.

#user html;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
            worker_connections  1024;
}


http {


#
# A virtual host using mix of IP-, name-, and port-based configuration
#

        proxy_set_header            Host            $http_host;
        proxy_set_header            X-Real-IP       $remote_addr;
        proxy_set_header            X-Forwared-For  $proxy_add_x_forwarded_for;

#
# The upstream VCSA hostname or IP address for port 9443
#
        upstream vcsa-9443 {
                  server 192.168.1.128:9443;
        }

#
# HTTP => HTTPS redirect
#
        server {
                listen        80;
                server_name   example.com;

                location / {
                        allow all;
                        return 302 https://$server_name$request_uri;
                }
        }

#
# Main HTTPS Reverse Proxy for the VCSA
#
        server {
                listen        443 ssl;
                listen        9443 ssl;
                server_name   example.com;

                ssl_certificate  /etc/letsencrypt/live/example.com/fullchain.pem;
                ssl_certificate_key  /etc/letsencrypt/live/example.com/privkey.pem;
                ssl_protocols  TLSv1 TLSv1.1 TLSv1.2;
                ssl_ciphers    HIGH:!aNULL:!MD5;
                keepalive_timeout 60;

                location /vsphere-client {
                        allow all;
                        proxy_set_header Host $http_host;
                        proxy_set_header Upgrade $http_upgrade;
                        proxy_set_header Connection "upgrade";
                        proxy_pass https://vcsa-9443;
                }
        }
}

The following line fixes the redirect issue. Now I’m getting a 404 error for /websso/SAML2/SSOSSL. The link it’s trying to go to looks just the same as when it’s working locally minus using the IP. Not yet working, but at least I know I’m definitely getting to the server from an external source.

proxy_redirect https://192.168.1.128 https://example.com;