diff --git a/app/controllers/integration/sipgate_controller.rb b/app/controllers/integration/sipgate_controller.rb
index 5fa0eb2b8..53768edc0 100644
--- a/app/controllers/integration/sipgate_controller.rb
+++ b/app/controllers/integration/sipgate_controller.rb
@@ -118,7 +118,10 @@ class Integration::SipgateController < ApplicationController
 
   def base_url
     http_type = Setting.get('http_type')
-    fqdn      = Setting.get('fqdn')
+    fqdn = Setting.get('sipgate_alternative_fqdn')
+    if fqdn.blank?
+      fqdn = Setting.get('fqdn')
+    end
     "#{http_type}://#{fqdn}/api/v1/sipgate"
   end
 
diff --git a/db/migrate/20181010000000_setting_add_sipgate_alternative_fqdn.rb b/db/migrate/20181010000000_setting_add_sipgate_alternative_fqdn.rb
new file mode 100644
index 000000000..512008d44
--- /dev/null
+++ b/db/migrate/20181010000000_setting_add_sipgate_alternative_fqdn.rb
@@ -0,0 +1,30 @@
+class SettingAddSipgateAlternativeFqdn < ActiveRecord::Migration[5.1]
+  def up
+
+    # return if it's a new setup
+    return if !Setting.find_by(name: 'system_init_done')
+
+    Setting.create_if_not_exists(
+      title: 'sipgate.io alternative fqdn',
+      name: 'sipgate_alternative_fqdn',
+      area: 'Integration::Sipgate::Expert',
+      description: 'Alternative FQDN for callbacks if you operate Zammad in internal network.',
+      options: {
+        form: [
+          {
+            display: '',
+            null: false,
+            name: 'sipgate_alternative_fqdn',
+            tag: 'input',
+          },
+        ],
+      },
+      state: '',
+      preferences: {
+        permission: ['admin.integration'],
+      },
+      frontend: false
+    )
+  end
+
+end
diff --git a/db/seeds/settings.rb b/db/seeds/settings.rb
index 094967f5f..c7cd1075e 100644
--- a/db/seeds/settings.rb
+++ b/db/seeds/settings.rb
@@ -3913,6 +3913,27 @@ Setting.create_if_not_exists(
   },
   frontend: false,
 )
+Setting.create_if_not_exists(
+  title: 'sipgate.io alternative fqdn',
+  name: 'sipgate_alternative_fqdn',
+  area: 'Integration::Sipgate::Expert',
+  description: 'Alternative FQDN for callbacks if you operate Zammad in internal network.',
+  options: {
+    form: [
+      {
+        display: '',
+        null: false,
+        name: 'sipgate_alternative_fqdn',
+        tag: 'input',
+      },
+    ],
+  },
+  state: '',
+  preferences: {
+    permission: ['admin.integration'],
+  },
+  frontend: false
+)
 Setting.create_if_not_exists(
   title: 'cti integration',
   name: 'cti_integration',
diff --git a/spec/requests/integration/sipgate_spec.rb b/spec/requests/integration/sipgate_spec.rb
index f88301419..bee8673ee 100644
--- a/spec/requests/integration/sipgate_spec.rb
+++ b/spec/requests/integration/sipgate_spec.rb
@@ -441,5 +441,24 @@ RSpec.describe 'Integration Sipgate', type: :request do
       expect(json_response['list'][4]['state']).to eq('hangup')
       expect(json_response['list'][5]['call_id']).to eq('1234567890-1')
     end
+
+    it 'alternative fqdn' do
+      Setting.set('sipgate_alternative_fqdn', 'external.host.example.com')
+
+      # inbound - I
+      params = 'event=newCall&direction=in&from=4912347114711&to=4930600000000&callId=4991155921769858278-1&user%5B%5D=user+1&user%5B%5D=user+2'
+      post '/api/v1/sipgate/in', params: params
+      expect(@response).to have_http_status(200)
+      on_hangup = nil
+      on_answer = nil
+      content = @response.body
+      response = REXML::Document.new(content)
+      response.elements.each('Response') do |element|
+        on_hangup = element.attributes['onHangup']
+        on_answer = element.attributes['onAnswer']
+      end
+      expect(on_hangup).to eq('http://external.host.example.com/api/v1/sipgate/in')
+      expect(on_answer).to eq('http://external.host.example.com/api/v1/sipgate/in')
+    end
   end
 end