writer role can't move to the other server but reader role can(mysql-mmm-1.2.6)

[soul]

eth0 Link encap:Ethernet HWaddr 00:15:17:8E:41:DE
          inet addr:10.3.1.92 Bcast:10.3.1.255 Mask:255.255.255.0

eth0 Link encap:Ethernet HWaddr 00:15:17:5C:A3:FD
          inet addr:10.3.1.100 Bcast:10.3.1.255 Mask:255.255.255.0

Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.144;), reader(10.3.1.145;), writer(10.3.1.146;)
  db2(10.3.1.92): master/ONLINE. Roles: None

  10.3.1.144 ether 00:15:17:5C:A3:FD C eth1
  10.3.1.145 ether 00:15:17:5C:A3:FD C eth1
  10.3.1.146 ether 00:15:17:5C:A3:FD C eth1
=================================================================================
  Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.144;), writer(10.3.1.146;)
  db2(10.3.1.92): master/ONLINE. Roles: reader(10.3.1.145;)

  10.3.1.145 ether 00:15:17:8E:41:DE C eth1
  10.3.1.146 ether 00:15:17:5C:A3:FD C eth1
  10.3.1.144 ether 00:15:17:5C:A3:FD C eth1
=================================================================================
Servers status:
  db1(10.3.1.100): master/ADMIN_OFFLINE. Roles: None
  db2(10.3.1.92): master/ONLINE. Roles: reader(10.3.1.144;), reader(10.3.1.145;), writer(10.3.1.146;)
10.3.1.144 ether 00:15:17:8E:41:DE C eth1
10.3.1.145 ether 00:15:17:8E:41:DE C eth1
10.3.1.146 (incomplete) eth1
==================================================================================
Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.145;)
  db2(10.3.1.92): master/ONLINE. Roles: reader(10.3.1.144;), writer(10.3.1.146;)
10.3.1.144 ether 00:15:17:8E:41:DE C eth1
10.3.1.145 ether 00:15:17:8E:41:DE C eth1
10.3.1.146 (incomplete) eth1
=====================================================
Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.144;), reader(10.3.1.145;), writer(10.3.1.146;)
  db2(10.3.1.92): master/ADMIN_OFFLINE. Roles: None
10.3.1.144 ether 00:15:17:5C:A3:FD C eth1
10.3.1.145 ether 00:15:17:8E:41:DE C eth1
10.3.1.146 ether 00:15:17:5C:A3:FD C eth1

-->in a little while

10.3.1.144 ether 00:15:17:5C:A3:FD C eth1
10.3.1.145 ether 00:15:17:5C:A3:FD C eth1
10.3.1.146 ether 00:15:17:5C:A3:FD C eth1

==========================================================
Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.144;), writer(10.3.1.146;)
  db2(10.3.1.92): master/ONLINE. Roles: reader(10.3.1.145;)
10.3.1.144 ether 00:15:17:8E:41:DE C eth1
10.3.1.145 ether 00:15:17:8E:41:DE C eth1
10.3.1.146 ether 00:15:17:5C:A3:FD C eth1

[root@dsrhf mmm]# ./sbin/mmm_control move_role writer db2
Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.144;)
  db2(10.3.1.92): master/ONLINE. Roles: reader(10.3.1.145;), writer(10.3.1.146;)
10.3.1.144 ether 00:15:17:8E:41:DE C eth1
10.3.1.145 ether 00:15:17:8E:41:DE C eth1
10.3.1.146 (incomplete) eth1
==================================================================================
[root@dsrhf mmm]# ./sbin/mmm_control move_role writer db1
Servers status:
  db1(10.3.1.100): master/ONLINE. Roles: reader(10.3.1.144;), writer(10.3.1.146;)
  db2(10.3.1.92): master/ONLINE. Roles: reader(10.3.1.145;)
10.3.1.144 ether 00:15:17:8E:41:DE C eth1
10.3.1.145 ether 00:15:17:8E:41:DE C eth1
10.3.1.146 ether 00:15:17:5C:A3:FD C eth1

why 146 is writer ,but the arp shows "incomplete", i have Tried several.
can you help me？