override-favicon-in-multisite.php

<?php

/*** Add a custom favicon for the admin area ***/
function custom_admin_favicon() {
  $url = ''; // Place the path to your dashboard icon here.
    echo '<link rel="Shortcut Icon" type="image/x-icon" href="' . $url . '" />';
  }
add_action( 'admin_head', 'custom_admin_favicon' );

/*** Add a custom default front end favicon ***/
function custom_default_favicon() {
  if ( ! has_site_icon()  && ! is_customize_preview() ) {
    $url = ''; // Place the path to your front icon here.
      echo '<link rel="Shortcut Icon" type="image/x-icon" href="' . $url . '" />';
    }
  }
add_action( 'wp_head', 'custom_default_favicon' );