ubuntu 12.04 校内网ipv6时好时坏，新人求助

:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:1f:16:31:1f:78
inet addr:180.201.10.58 Bcast:180.201.11.255 Mask:255.255.254.0
inet6 addr: 2001:da8:7000:7008:21f:16ff:fe31:1f78/64 Scope:Global
inet6 addr: fec0::a:21f:16ff:fe31:1f78/64 Scope:Site
inet6 addr: 2002:b4c9:a93:a:21f:16ff:fe31:1f78/64 Scope:Global
inet6 addr: fe80::21f:16ff:fe31:1f78/64 Scope:Link
inet6 addr: 2001:da8:7000:7008:85af:4677:fb96:1915/64 Scope:Global
inet6 addr: fec0::a:85af:4677:fb96:1915/64 Scope:Site
inet6 addr: 2002:b4c9:a93:a:85af:4677:fb96:1915/64 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:36660 errors:0 dropped:1 overruns:0 frame:0
TX packets:6171 errors:0 dropped:0 overruns:0 carrier:1
collisions:0 txqueuelen:1000
RX bytes:8394836 (8.3 MB) TX bytes:815668 (815.6 KB)
Interrupt:45

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:657 errors:0 dropped:0 overruns:0 frame:0
TX packets:657 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:70789 (70.7 KB) TX bytes:70789 (70.7 KB)
校内网ipv6怎么时好时坏，同宿舍的能连上，为什么我的要讲究个概率？？？