diff --git a/centos.php b/centos.php
index 2e540b7..6b8f6d4 100644
--- a/centos.php
+++ b/centos.php
@@ -51,6 +51,9 @@
     $mirrors = array('http://vault.centos.org/');
 } else {
     $mirrors = get_centos_mirrors($release, $arch);
+    if(empty($mirrors)) {
+        $mirrors = array('http://mirror.centos.org/centos');
+    }
 }
 
 foreach($mirrors as $mirror) {
diff --git a/config.php b/config.php
index a33e516..88af9fa 100644
--- a/config.php
+++ b/config.php
@@ -50,9 +50,12 @@
 );
 
 
-// Alternative architectures:
-// - stable goes to mirror,
-// - development goes to packages.nethserver.org
+// Architectures:
+//
+// - "stable" goes to the official NS mirror infrastructure
+//
+// - "development" goes to mirror.nethserver.org
+//
 $stable_arches = array(
     'x86_64',
 );
diff --git a/cron.php b/cron.php
index cd2d154..362438f 100644
--- a/cron.php
+++ b/cron.php
@@ -32,7 +32,12 @@
 
 $major_releases = array_unique(preg_replace('/^(\d).*/', '$1', $stable_releases));
 foreach($major_releases as $release) {
-    foreach($stable_arches as $arch) {
+    foreach(array_merge($stable_arches, $development_arches) as $arch) {
+        // skip altarch for 6 branch
+        if($release == '6' && $arch != 'x86_64') {
+            continue;
+        }
+
         $status = refresh_centos_mirrors_cache($ce_mirror_countries, $release, $arch);
         if( ! $status) {
             error_log("[ERROR] Failed to write $release $arch cache file");
diff --git a/mirrorcache.php b/mirrorcache.php
index e893ebd..a8c6193 100644
--- a/mirrorcache.php
+++ b/mirrorcache.php
@@ -77,6 +77,5 @@ function get_centos_mirrors($release, $arch)
         $mirrors = array();
     }
 
-    // fallback to default mirrorlist or return valid entries
-    return empty($mirrors) ? array('http://mirror.centos.org/centos') : $mirrors;
+    return $mirrors;
 }
diff --git a/nethserver.php b/nethserver.php
index 903d931..4f09644 100644
--- a/nethserver.php
+++ b/nethserver.php
@@ -91,10 +91,22 @@
     // map to real repository name, extracting the $repo_suffix (required by SCLo):
     list($repo, $repo_suffix) = array_merge(explode('-', $ce_repos[$repo], 2), array(''));
     if(in_array($nsrelease, $vault_releases)) {
-        $mirrors = array('http://vault.centos.org');
+        // CentOS versions served by vault.centos.org
+        if($arch == 'x86_64') {
+            $mirrors = array('http://vault.centos.org/centos');
+        } else {
+            $mirrors = array('http://vault.centos.org/altarch');
+        }
     } else {
         // CentOS versions served by upstream mirror infrastructure
         $mirrors = get_centos_mirrors($release, $arch);
+        if(empty($mirrors)) {
+            if($arch == 'x86_64') {
+                $mirrors = array('http://mirror.centos.org/centos');
+            } else {
+                $mirrors = array('http://mirror.centos.org/altarch');
+            }
+        }
     }
 } else {
     // Serverd only by the NethServer master mirror