Drupal 8: Multi-sites in subdirectories not working
Download latest  D8 version. 
Extract and navigate into the
directory: /drupal/sites/
Create sites.php duplicating example.sites.php
Add the code to sites.php

$sites = array(
      'dogs.multisite.local' =&gt; 'dogs',
      'multisite.local.cats' =&gt; 'cats',
    );
Create two folders named 'cats' and 'dogs' on the sites folder.

/drupal/sites/dogs/
/drupal/sites/cats/

The /drupal/sites/default/ site will have default files we need to copy into each of our sites. Copy these files using the cp command in the sites directory:

cp default/default.settings.php dogs/settings.php
cp default/default.settings.php cats/settings.php    
cp default/default.services.yml dogs/services.yml
cp default/default.services.yml cats/services.yml

Setup virtualhost

hosts

 127.0.0.1  multisite.local


httpd-vhosts.conf

&lt;VirtualHost *:80&gt;
ServerAdmin webmaster@multisite.local
DocumentRoot "/opt/lampp/htdocs/drupal"
ServerName multisite.local
ServerAlias    *.multisite.local multisite.local.*
ErrorLog "logs/multisite.local-error_log"
CustomLog "logs/multisite.local-access_log" common
&lt;/VirtualHost&gt;

Once it is done, you can start the installation of your new website in a multisite context from the urls:

   http://dogs.multisite.local/
   http://multisite.local.cats/