diff --git a/src/wp-admin/includes/network.php b/src/wp-admin/includes/network.php
index da7aec3..b008176 100644
--- a/src/wp-admin/includes/network.php
+++ b/src/wp-admin/includes/network.php
@@ -52,13 +52,13 @@ function allow_subdomain_install() {
  */
 function allow_subdirectory_install() {
 	global $wpdb;
-		/**
-		 * Filters whether to enable the subdirectory installation feature in Multisite.
-		 *
-		 * @since 3.0.0
-		 *
-		 * @param bool $allow Whether to enable the subdirectory installation feature in Multisite. Default is false.
-		 */
+	/**
+	 * Filters whether to enable the subdirectory installation feature in Multisite.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param bool $allow Whether to enable the subdirectory installation feature in Multisite. Default is false.
+	 */
 	if ( apply_filters( 'allow_subdirectory_install', false ) ) {
 		return true;
 	}
@@ -133,7 +133,14 @@ function network_step1( $errors = false ) {
 
 	$hostname  = get_clean_basedomain();
 	$has_ports = strstr( $hostname, ':' );
-	if ( ( false !== $has_ports && ! in_array( $has_ports, array( ':80', ':443' ) ) ) ) {
+	/**
+	 * Filters allowed HTTP ports in Multisite.
+	 *
+	 * @since 5.0.0
+	 *
+	 * @param array $allowed_ports The allowed ports. Default is [ ':80', ':443' ].
+	 */
+	if ( ( false !== $has_ports && ! in_array( $has_ports, apply_filters( 'allowed_multisite_ports', array( ':80', ':443' ) ) ) ) ) {
 		echo '<div class="error"><p><strong>' . __( 'ERROR:' ) . '</strong> ' . __( 'You cannot install a network of sites with your server address.' ) . '</p></div>';
 		echo '<p>' . sprintf(
 			/* translators: %s: port number */
diff --git a/src/wp-admin/network/site-info.php b/src/wp-admin/network/site-info.php
index 83e05ae..facec76 100644
--- a/src/wp-admin/network/site-info.php
+++ b/src/wp-admin/network/site-info.php
@@ -67,9 +67,12 @@ if ( isset( $_REQUEST['action'] ) && 'update-site' == $_REQUEST['action'] ) {
 
 		$blog_data['scheme'] = $update_parsed_url['scheme'];
 		$blog_data['domain'] = $update_parsed_url['host'];
+		// Add port (if it's in allowed list)
+		if ( ! empty( $update_parsed_url['port'] && in_array( ':' . $update_parsed_url['port'], apply_filters( 'allowed_multisite_ports', array( ':80', ':443' ) ) ) ) ) {
+			$blog_data['domain'] .= ':' . $update_parsed_url['port'];
+		}
 		$blog_data['path']   = $update_parsed_url['path'];
 	}
-
 	$existing_details     = get_site( $id );
 	$blog_data_checkboxes = array( 'public', 'archived', 'spam', 'mature', 'deleted' );
 	foreach ( $blog_data_checkboxes as $c ) {
diff --git a/src/wp-includes/ms-functions.php b/src/wp-includes/ms-functions.php
index 984a69c..962998e 100644
--- a/src/wp-includes/ms-functions.php
+++ b/src/wp-includes/ms-functions.php
@@ -1272,7 +1272,9 @@ function wpmu_create_blog( $domain, $path, $title, $user_id, $meta = array(), $n
 	);
 	$meta     = wp_parse_args( $meta, $defaults );
 
+	add_filter( 'sanitize_user', 'wpmu_sanitize_domain_filter', 1, 3 );
 	$domain = preg_replace( '/\s+/', '', sanitize_user( $domain, true ) );
+	remove_filter( 'sanitize_user', 'wpmu_sanitize_domain_filter', 1, 3 );
 
 	if ( is_subdomain_install() ) {
 		$domain = str_replace( '@', '', $domain );
@@ -1339,6 +1341,23 @@ function wpmu_create_blog( $domain, $path, $title, $user_id, $meta = array(), $n
 }
 
 /**
+ * Callback for 'sanitize_user' filter allowing ports in domain string.
+ *
+ * @since 5.0.0
+ *
+ * @param string $domain       Sanitized domain.
+ * @param string $raw_domain   The domain prior to sanitization.
+ * @param bool   $strict       Whether to limit the sanitization to specific characters. Default false.
+ */
+function wpmu_sanitize_domain_filter ( $domain, $raw_domain, $strict ) {
+	$port = parse_url( $raw_domain, PHP_URL_PORT );
+	if ( ! empty($port) && in_array( ':' . $port, apply_filters( 'allowed_multisite_ports', array( ':80', ':443' ) ) ) ) {
+		$domain = preg_replace( "/{$port}$/", ':' . $port, $domain );
+	}
+	return $domain;
+}
+
+/**
  * Notifies the network admin that a new site has been activated.
  *
  * Filter {@see 'newblog_notify_siteadmin'} to change the content of