diff --git a/group_vars/matrix_servers b/group_vars/matrix_servers
index 305d8044..864f7702 100755
--- a/group_vars/matrix_servers
+++ b/group_vars/matrix_servers
@@ -29,6 +29,14 @@ matrix_homeserver_container_url: |-
     }[matrix_homeserver_implementation]
   }}
 
+matrix_homeserver_container_federation_url: |-
+  {{
+    'http://matrix-nginx-proxy:12088' if matrix_nginx_proxy_enabled else {
+      'synapse': ('http://matrix-synapse:'+ matrix_synapse_container_federation_api_plain_port|string),
+      'dendrite': ('http://matrix-dendrite:' + matrix_dendrite_http_bind_port|string),
+    }[matrix_homeserver_implementation]
+  }}
+
 ######################################################################
 #
 # /matrix-base
@@ -1131,7 +1139,7 @@ matrix_dimension_container_image_self_build: "{{ matrix_architecture != 'amd64'
 # the Dimension HTTP port to the local host.
 matrix_dimension_container_http_host_bind_port: "{{ '' if matrix_nginx_proxy_enabled else '127.0.0.1:8184' }}"
 
-matrix_dimension_homeserver_federationUrl: "http://matrix-synapse:{{matrix_synapse_container_federation_api_plain_port|string}}"
+matrix_dimension_homeserver_federationUrl: "{{ matrix_homeserver_container_federation_url }}"
 
 matrix_integration_manager_rest_url: "{{ matrix_dimension_integrations_rest_url if matrix_dimension_enabled else None }}"
 matrix_integration_manager_ui_url: "{{ matrix_dimension_integrations_ui_url if matrix_dimension_enabled else None }}"
diff --git a/roles/matrix-base/defaults/main.yml b/roles/matrix-base/defaults/main.yml
index dc273afd..be403de7 100644
--- a/roles/matrix-base/defaults/main.yml
+++ b/roles/matrix-base/defaults/main.yml
@@ -103,11 +103,16 @@ matrix_ntpd_service: "{{ 'systemd-timesyncd' if (ansible_distribution == 'CentOS
 
 matrix_homeserver_url: "https://{{ matrix_server_fqn_matrix }}"
 
-# Specifies where the homeserver is on the container network.
-# Where this is depends on whether there's a reverse-proxy in front of it, etc.
+# Specifies where the homeserver's Client-Server API is on the container network.
+# Where this is depends on whether there's a reverse-proxy in front of the homeserver, which homeserver it is, etc.
 # This likely gets overriden elsewhere.
 matrix_homeserver_container_url: ""
 
+# Specifies where the homeserver's Federation API is on the container network.
+# Where this is depends on whether there's a reverse-proxy in front of the homeserver, which homeserver it is, etc.
+# This likely gets overriden elsewhere.
+matrix_homeserver_container_federation_url: ""
+
 matrix_identity_server_url: ~
 
 matrix_integration_manager_rest_url: ~
diff --git a/roles/matrix-base/tasks/validate_config.yml b/roles/matrix-base/tasks/validate_config.yml
index 8bb3fca0..84ef2f06 100644
--- a/roles/matrix-base/tasks/validate_config.yml
+++ b/roles/matrix-base/tasks/validate_config.yml
@@ -6,4 +6,5 @@
       You need to define a required configuration setting (`{{ item }}`) for using this playbook.
   when: "vars[item] == ''"
   with_items:
-    - "matrix_homeserver_container_url"
\ No newline at end of file
+    - "matrix_homeserver_container_url"
+    - "matrix_homeserver_container_federation_url"