diff --git a/lib/uri/generic.rb b/lib/uri/generic.rb
index bdd3666..683149f 100644
--- a/lib/uri/generic.rb
+++ b/lib/uri/generic.rb
@@ -10,7 +10,6 @@
 
 require_relative 'common'
 autoload :IPSocket, 'socket'
-autoload :IPAddr, 'ipaddr'
 
 module URI
 
@@ -1564,15 +1563,54 @@ def self.use_proxy?(hostname, addr, port, no_proxy) # :nodoc:
             return false if dothostname.end_with?(".#{p_host.downcase}")
           end
           if addr
-            begin
-              return false if IPAddr.new(p_host).include?(addr)
-            rescue IPAddr::InvalidAddressError
-              next
-            end
+            return false if addr == p_host || in_ip_range?(addr, p_host)
           end
         end
       }
       true
     end
+
+    private
+
+    def self.expand_ipv6(ip)
+      if ip.include?('::')
+        parts = ip.split('::')
+        left = parts[0].split(':')
+        right = parts[1] ? parts[1].split(':') : []
+        middle = ['0'] * (8 - left.size - right.size)
+        (left + middle + right).join(':')
+      else
+        ip
+      end
+    end
+    
+    def self.ip_to_i(ip)
+      if ip.include?(':')
+        expanded_ip = expand_ipv6(ip)
+        segments = expanded_ip.split(':').map { |seg| seg.rjust(4, '0') }
+        hex_ip = segments.join
+        hex_ip.to_i(16)
+      else
+        ip.split('.').map(&:to_i).pack('C*').unpack1('N')
+      end
+    end
+    
+    def self.in_ip_range?(ip, range)
+      return false unless range.include?('/')
+    
+      base, bits = range.split('/')
+      bits = bits.to_i
+    
+      if base.include?(':')
+        # IPv6
+        expanded_base = expand_ipv6(base)
+        mask = (1 << 128) - (1 << (128 - bits))
+        (ip_to_i(ip) & mask) == (ip_to_i(expanded_base) & mask)
+      else
+        # IPv4
+        mask = (0xFFFFFFFF << (32 - bits)) & 0xFFFFFFFF
+        (ip_to_i(ip) & mask) == (ip_to_i(base) & mask)
+      end
+    end
   end
 end