MTU问题

zhou492802882

<RT2>dis ip int   
GigabitEthernet0/0/0 current state :UP
Line protocol current state :UP
Internet Address is 12.1.1.2/24 Primary
Broadcast address : 12.1.1.255
The Maximum Transmit Unit : 1500 bytes
那么现在
<RT2>ping -f -s 1500 12.1.1.1
  PING 12.1.1.1: 1500  data bytes, press CTRL_C to break
    Request time out
    Request time out
怎么会不通呢？