diff --git a/app/controllers/ip_addresses_controller.rb b/app/controllers/ip_addresses_controller.rb
index a1f382f97..c910cecf0 100644
--- a/app/controllers/ip_addresses_controller.rb
+++ b/app/controllers/ip_addresses_controller.rb
@@ -4,10 +4,10 @@ class IpAddressesController < ApplicationController
 
   def index
     if search_params[:group_by] == "ip_addr"
-      @ip_addresses = IpAddress.search(search_params).group_by_ip_addr
+      @ip_addresses = IpAddress.search(search_params).group_by_ip_addr(search_params[:ipv4_masklen], search_params[:ipv6_masklen]).paginate(params[:page], limit: params[:limit] || 1000)
       respond_with(@ip_addresses)
     elsif search_params[:group_by] == "user"
-      @ip_addresses = IpAddress.search(search_params).group_by_user
+      @ip_addresses = IpAddress.includes(:user).search(search_params).group_by_user.paginate(params[:page], limit: params[:limit] || 1000)
       respond_with(@ip_addresses)
     else
       @ip_addresses = IpAddress.includes(:user, :model).paginated_search(params)
diff --git a/app/models/ip_address.rb b/app/models/ip_address.rb
index ecb9c9580..33c35fe06 100644
--- a/app/models/ip_address.rb
+++ b/app/models/ip_address.rb
@@ -14,14 +14,31 @@ class IpAddress < ApplicationRecord
     q.order(created_at: :desc)
   end
 
-  def self.group_by_ip_addr
-    group(:ip_addr).select("ip_addr, COUNT(*) AS count_all").reorder("count_all DESC, ip_addr")
+  def self.group_by_ip_addr(ipv4_masklen = nil, ipv6_masklen = nil)
+    ipv4_masklen ||= 32
+    ipv6_masklen ||= 128
+
+    q = select(sanitize_sql([<<~SQL, ipv4_masklen, ipv6_masklen]))
+      CASE
+        WHEN family(ip_addr) = 4
+        THEN network(set_masklen(ip_addr, ?))
+        ELSE network(set_masklen(ip_addr, ?))
+      END AS ip_addr,
+      COUNT(*) AS count_all
+    SQL
+
+    q.group("1").reorder("count_all DESC, ip_addr")
   end
 
   def self.group_by_user
     group(:user_id).select("user_id, COUNT(*) AS count_all").reorder("count_all DESC, user_id")
   end
 
+  def to_s
+    # include the subnet mask only when the IP denotes a subnet.
+    ip_addr.size > 1 ? ip_addr.to_string : ip_addr.to_s
+  end
+
   def readonly?
     true
   end
diff --git a/app/views/ip_addresses/_index_by_ip_addr.html.erb b/app/views/ip_addresses/_index_by_ip_addr.html.erb
index 27f58645a..bd7518593 100644
--- a/app/views/ip_addresses/_index_by_ip_addr.html.erb
+++ b/app/views/ip_addresses/_index_by_ip_addr.html.erb
@@ -9,10 +9,10 @@
     <% @ip_addresses.each do |ip| %>
       <tr>
         <td>
-          <%= link_to ip.ip_addr, ip_addresses_path(search: { ip_addr: ip.ip_addr }) %>
-          <%= link_to "»", ip_addresses_path(search: { ip_addr: ip.ip_addr, group_by: "user" }) %>
+          <%= link_to ip.to_s, ip_addresses_path(search: { ip_addr: ip.to_s }) %>
+          <%= link_to "»", ip_addresses_path(search: { ip_addr: ip.to_s, group_by: "user" }) %>
         </td>
-        <td><%= link_to ip.count_all, ip_addresses_path(search: { ip_addr: ip.ip_addr }) %></td>
+        <td><%= link_to ip.count_all, ip_addresses_path(search: { ip_addr: ip.to_s }) %></td>
       </tr>
     <% end %>
   </tbody>
diff --git a/app/views/ip_addresses/index.html.erb b/app/views/ip_addresses/index.html.erb
index 1f11d3d65..d5afb1d6a 100644
--- a/app/views/ip_addresses/index.html.erb
+++ b/app/views/ip_addresses/index.html.erb
@@ -7,6 +7,10 @@
       <%= f.input :created_at, label: "Date", input_html: { value: params[:search][:created_at] } %>
       <%= f.input :model_type, label: "Source", collection: IpAddress.model_types, include_blank: true, selected: params[:search][:model_type] %>
       <%= f.input :group_by, label: "Group By", collection: [["User", "user"], ["IP Address", "ip_addr"]], include_blank: true, selected: params[:search][:group_by] %>
+      <% if params[:search][:group_by] == "ip_addr" %>
+        <%= f.input :ipv4_masklen, label: "IPv4 Subnet", collection: [["/32", 32], ["/24", 24], ["/16", 16], ["/8", 8]], include_blank: false, selected: params[:search][:ipv4_masklen], hint: "Lower to group together IPs with the same prefix."  %>
+        <%= f.input :ipv6_masklen, label: "IPv6 Subnet", collection: [["/128", 128], ["/80", 80], ["/64", 64], ["/48", 48]], include_blank: false, selected: params[:search][:ipv6_masklen] %>
+      <% end %>
       <%= f.submit "Search" %>
     <% end %>