diff --git a/pr-preview/pr-9/404.html b/pr-preview/pr-9/404.html
index d3c3146..d711af5 100644
--- a/pr-preview/pr-9/404.html
+++ b/pr-preview/pr-9/404.html
@@ -911,7 +911,7 @@
         
   
   <span class="md-ellipsis">
-    Prefix length
+    Prefix length filtering
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diff --git a/pr-preview/pr-9/contribution/example-networks/index.html b/pr-preview/pr-9/contribution/example-networks/index.html
index f7793d3..c277ad6 100644
--- a/pr-preview/pr-9/contribution/example-networks/index.html
+++ b/pr-preview/pr-9/contribution/example-networks/index.html
@@ -1091,7 +1091,7 @@
         
   
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-    Prefix length
+    Prefix length filtering
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diff --git a/pr-preview/pr-9/contribution/formatting/index.html b/pr-preview/pr-9/contribution/formatting/index.html
index ff4b655..4f3afc2 100644
--- a/pr-preview/pr-9/contribution/formatting/index.html
+++ b/pr-preview/pr-9/contribution/formatting/index.html
@@ -1003,7 +1003,7 @@
         
   
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-    Prefix length
+    Prefix length filtering
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diff --git a/pr-preview/pr-9/contribution/index.html b/pr-preview/pr-9/contribution/index.html
index 8a427eb..0f725b1 100644
--- a/pr-preview/pr-9/contribution/index.html
+++ b/pr-preview/pr-9/contribution/index.html
@@ -932,7 +932,7 @@
         
   
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-    Prefix length
+    Prefix length filtering
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diff --git a/pr-preview/pr-9/guides/control_plane_protection/index.html b/pr-preview/pr-9/guides/control_plane_protection/index.html
index 0ce9b38..c376d9a 100644
--- a/pr-preview/pr-9/guides/control_plane_protection/index.html
+++ b/pr-preview/pr-9/guides/control_plane_protection/index.html
@@ -934,7 +934,7 @@
         
   
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-    Prefix length
+    Prefix length filtering
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diff --git a/pr-preview/pr-9/guides/control_plane_protection/protect_your_bgp_session/index.html b/pr-preview/pr-9/guides/control_plane_protection/protect_your_bgp_session/index.html
index af3eb49..6066b0f 100644
--- a/pr-preview/pr-9/guides/control_plane_protection/protect_your_bgp_session/index.html
+++ b/pr-preview/pr-9/guides/control_plane_protection/protect_your_bgp_session/index.html
@@ -1000,7 +1000,7 @@
         
   
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-    Prefix length
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diff --git a/pr-preview/pr-9/guides/forwarding_filter/index.html b/pr-preview/pr-9/guides/forwarding_filter/index.html
index 0298ec5..12870f5 100644
--- a/pr-preview/pr-9/guides/forwarding_filter/index.html
+++ b/pr-preview/pr-9/guides/forwarding_filter/index.html
@@ -934,7 +934,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/index.html b/pr-preview/pr-9/guides/index.html
index 6c73d32..bd6217d 100644
--- a/pr-preview/pr-9/guides/index.html
+++ b/pr-preview/pr-9/guides/index.html
@@ -932,7 +932,7 @@
         
   
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-    Prefix length
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/as_path_length/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/as_path_length/index.html
index 0d4941d..53e9b02 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/as_path_length/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/as_path_length/index.html
@@ -993,7 +993,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/blackhole/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/blackhole/index.html
index 94ec6e9..8468434 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/blackhole/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/blackhole/index.html
@@ -929,7 +929,7 @@
         
   
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+    Prefix length filtering
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/bogon_asn/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/bogon_asn/index.html
index af38fed..3362791 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/bogon_asn/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/bogon_asn/index.html
@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/bogon_prefixes/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/bogon_prefixes/index.html
index 9f341e3..a3ccda5 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/bogon_prefixes/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/bogon_prefixes/index.html
@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/default_route/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/default_route/index.html
index 6639dfc..e1ee6c4 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/default_route/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/default_route/index.html
@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/graceful_shutdown/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/graceful_shutdown/index.html
index c971f50..e851f87 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/graceful_shutdown/index.html
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@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/index.html
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--- a/pr-preview/pr-9/guides/route_filtering/inbound/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/index.html
@@ -936,7 +936,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/maintenance_switch/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/maintenance_switch/index.html
index 0798333..9466fe6 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/maintenance_switch/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/maintenance_switch/index.html
@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/max_prefix/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/max_prefix/index.html
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--- a/pr-preview/pr-9/guides/route_filtering/inbound/max_prefix/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/max_prefix/index.html
@@ -936,7 +936,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/number_of_bgp_communities/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/number_of_bgp_communities/index.html
index 3872cd2..8629b4d 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/number_of_bgp_communities/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/number_of_bgp_communities/index.html
@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/own_bgp_communities/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/own_bgp_communities/index.html
index 0034b44..06cb7e5 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/own_bgp_communities/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/own_prefix/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/own_prefix/index.html
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--- a/pr-preview/pr-9/guides/route_filtering/inbound/own_prefix/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/peer_locking/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/peer_locking/index.html
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--- a/pr-preview/pr-9/guides/route_filtering/inbound/peer_locking/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/peering_lan/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/peering_lan/index.html
index aed7b84..a855be6 100644
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@@ -929,7 +929,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/prefix_length/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/prefix_length/index.html
index 2524566..fb1e857 100644
--- a/pr-preview/pr-9/guides/route_filtering/inbound/prefix_length/index.html
+++ b/pr-preview/pr-9/guides/route_filtering/inbound/prefix_length/index.html
@@ -20,7 +20,7 @@
     
     
       
-        <title>Prefix length - DENOG Routing Guide</title>
+        <title>Prefix length filtering - DENOG Routing Guide</title>
       
     
     
@@ -67,6 +67,11 @@
     <label class="md-overlay" for="__drawer"></label>
     <div data-md-component="skip">
       
+        
+        <a href="#prefix-length-filtering" class="md-skip">
+          Skip to content
+        </a>
+      
     </div>
     <div data-md-component="announce">
       
@@ -99,7 +104,7 @@
         <div class="md-header__topic" data-md-component="header-topic">
           <span class="md-ellipsis">
             
-              Prefix length
+              Prefix length filtering
             
           </span>
         </div>
@@ -923,12 +928,14 @@
       <input class="md-nav__toggle md-toggle" type="checkbox" id="__toc">
       
       
+        
+      
       
       <a href="./" class="md-nav__link md-nav__link--active">
         
   
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+    Prefix length filtering
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@@ -1299,6 +1306,8 @@
   
   
   
+    
+  
   
 </nav>
                   </div>
@@ -1329,9 +1338,40 @@
   
 
 
-  <h1>Prefix length</h1>
-
-
+<h1 id="prefix-length-filtering">Prefix length filtering</h1>
+<p>Normally (there are exceptions), prefixes are announced in certain minimum and maximum lengths in the global Internet routing table. Currently, they are:</p>
+<ul>
+<li><strong>IPv4, minimum size</strong> is /24. No smaller networks should be announced. Possible exceptions: \Gls{blackholing}, or an announcement in combination with a NO-EXPORT community set from a customer to his upstream.</li>
+<li><strong>IPv6, minimum size</strong> is /48. Same exceptions as within IPv4.</li>
+<li><strong>IPv4, maximum size</strong> is a /8. Larger networks are not announced. Depending on your set-up, you might want to accept the default-route 0.0.0.0/0 from your upstream providers.</li>
+<li><strong>IPv6, maximum size</strong> is currently a /16 (please take this with a grain of salt, this number might already have changed). The remark about accepting a default-route ::0 is the same.</li>
+</ul>
+<p>Configuration examples:</p>
+<div class="tabbed-set tabbed-alternate" data-tabs="1:1"><input checked="checked" id="__tabbed_1_1" name="__tabbed_1" type="radio" /><div class="tabbed-labels"><label for="__tabbed_1_1">Cisco IOS</label></div>
+<div class="tabbed-content">
+<div class="tabbed-block">
+<p>Using an <em>unwanted</em> prefix-list you can add  more prefixes to it that you not want. This shortens your configuration but might also decrease readability.
+```
+ip prefix-list ipv4-unwanted permit 0.0.0.0/0 ge 25 le 32
+ip prefix-list ipv4-unwanted permit 0.0.0.0/0 ge 1 le 7
+!
+route-map upstream-in-v4 deny 50
+    match ip address prefix-list ipv4-unwanted
+!
+ipv6 prefix-list ipv6-unwanted permit ::/0 ge 49 le 128
+ipv6 prefix-list ipv6-unwanted permit ::/0 ge 0 le 16
+!
+route-map upstream-in-v6 deny 45
+    match ipv6 address prefix-list ipv6-unwanted
+!
+router bgp 64500
+    neighbor 198.51.100.1 route-map upstream-in-v4 in
+    !
+    neighbor 2001:db8::1 route-map upstream-in-v6 in
+    !</p>
+</div>
+</div>
+</div>
 
 
 
diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/require_policy/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/require_policy/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/rpki/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/rpki/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/set_own_informational_bgp_communities/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/set_own_informational_bgp_communities/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/inbound/tier1_asn/index.html b/pr-preview/pr-9/guides/route_filtering/inbound/tier1_asn/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/outbound/customer_prefix/index.html b/pr-preview/pr-9/guides/route_filtering/outbound/customer_prefix/index.html
index 4124f02..896b252 100644
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diff --git a/pr-preview/pr-9/guides/route_filtering/outbound/index.html b/pr-preview/pr-9/guides/route_filtering/outbound/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/outbound/maintenance_switch/index.html b/pr-preview/pr-9/guides/route_filtering/outbound/maintenance_switch/index.html
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diff --git a/pr-preview/pr-9/guides/route_filtering/outbound/max_prefix/index.html b/pr-preview/pr-9/guides/route_filtering/outbound/max_prefix/index.html
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@@ -924,7 +924,7 @@
         
   
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+    Prefix length filtering
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diff --git a/pr-preview/pr-9/guides/route_filtering/outbound/own_prefix/index.html b/pr-preview/pr-9/guides/route_filtering/outbound/own_prefix/index.html
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@@ -924,7 +924,7 @@
         
   
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diff --git a/pr-preview/pr-9/guides/route_filtering/outbound/well_known_communities_traffic_engineering/index.html b/pr-preview/pr-9/guides/route_filtering/outbound/well_known_communities_traffic_engineering/index.html
index bf64274..4d4fbd3 100644
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+++ b/pr-preview/pr-9/guides/route_filtering/outbound/well_known_communities_traffic_engineering/index.html
@@ -919,7 +919,7 @@
         
   
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index 922053f..4db3949 100644
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@@ -928,7 +928,7 @@
         
   
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diff --git a/pr-preview/pr-9/sitemap.xml.gz b/pr-preview/pr-9/sitemap.xml.gz
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@@ -918,7 +918,7 @@
         
   
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+    Prefix length filtering
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