Floating Static route (with AD255)

floatint static routes with AD 255 does not work. Why??

Rack1R4#sh run | i ip route
ip route 150.1.5.0 255.255.255.0 155.1.45.5
ip route 150.1.5.0 255.255.255.0 Serial0/0.1 255
Rack1R4#sh ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            204.12.1.4      YES NVRAM  up                    up     
Serial0/0                  unassigned      YES NVRAM  up                    up     
Serial0/0.1                155.1.0.4       YES NVRAM  up                    up     
FastEthernet0/1            155.1.146.4     YES NVRAM  up                    up     
Serial0/1                  155.1.45.4      YES NVRAM  administratively down down   
Loopback0                  150.1.4.4       YES NVRAM  up                    up     

 Rack1R4#sh ip route 150.1.5.0
% Subnet not in table



Rack1R4(config)#ip route 150.1.5.0 255.255.255.0 155.1.0.5 254

Rack1R4#sh ip route 150.1.5.0
Routing entry for 150.1.5.0/24
  Known via "static", distance 254, metric 0
  Routing Descriptor Blocks:
  * 155.1.0.5
      Route metric is 0, traffic share count is 1