Gitlab can't access outside local ip

i have already installed GitLab Community Edition 8.3.2 with omnibus installed and running well if access from locally,
when im installed public ip in my server, gitlab can’t access and return unreachable,
im trying to debug with installed apache with port 8008, and running well if access from public and local.

i also have done config firewall,config external_url, and doesn’t solve the problem,
how to fix access gitlab from public ip ?

here my gitlab environtment info

System information
System: CentOS 6.6
Current User: git
Using RVM: no
Ruby Version: 2.1.7p400
Gem Version: 2.5.1
Bundler Version:1.10.6
Rake Version: 10.4.2
Sidekiq Version:4.0.1

GitLab information
Version: 8.3.2
Revision: fbb8b6e
Directory: /opt/gitlab/embedded/service/gitlab-rails
DB Adapter: postgresql
URL: http://x.x.x.
HTTP Clone URL: http://x.x.x/some-group/some-project.git
SSH Clone URL: git@x.x.x:some-group/some-project.git
Using LDAP: no
Using Omniauth: yes
Omniauth Providers: bitbucket

GitLab Shell
Version: 2.6.9
Repositories: /var/opt/gitlab/git-data/repositories
Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks/
Git: /opt/gitlab/embedded/bin/git

How is your server’s public IP address configured? Is it an address on the server itself, or is it on a router or separate firewall device? If the router/firewall has the public IP, is forwarding set up correctly? What manufacturer and model are the router/firewall? Who is your Internet Service Provider? Are you running this on a physical server or a virtual one?

Please answer those questions, and provide any other information that is similar to them which might be useful.