Vista On/Off LAN NIC IPv6 Option cause ISATAP packet flow interrup

ISATAP is short for Intra-Site Automatic Tunnel Addressing Protocol. It's
described in RFC 5214(March 2008).
ISATAP allow dual-stack nodes use ISATAP to automatically tunnel IPv6
packets in IPv4.
Windows provide ISATAP support since Windows XP. Configuration can be set in
[netsh interface ipv6 isatap].

The problem is, when Enable/Disable IPv6 support option in LAN NIC under
Windows Vista, data flow in ISATAP tunnel will stop for a while, sometimes it
will even be interrupt. It is not happen in XP or 2003.
As there is no IPv6 native router in LAN, IPv6 packets are all tunnel in
ipv4. Data flow should not be affect by LAN Native IPv6 support Option.

Vista Version 6.0(Build 6000), running as guest os in vmware server 1.0.5

Network application interruption error output example,
telnet client tells:" Connection to host lost."
iperf ipv6 client tells:"write failed: Connection reset by peer\n read on
server close failed: Connection reset by peer"

I tried to record route table, usint command " route print -6 | find
"::/0"". It seems that IPv6 default gateway to ISATAP tunnel server is lost
during LAN IPv6 Option modification.
When we disable IPv6 support in LAN,
C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>route print -6 | find "::/0"

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150




When Enable IPv6 in LAN:

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>route print -6 | find "::/0"

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150
9 18 ::/0 On-link

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150
9 18 ::/0 On-link

C:\Users\John>route print -6 | find "::/0"
9 18 ::/0 On-link

C:\Users\John>route print -6 | find "::/0"
9 18 ::/0 On-link

C:\Users\John>route print -6 | find "::/0"

C:\Users\John>route print -6 | find "::/0"
9 18 ::/0 On-link

C:\Users\John>route print -6 | find "::/0"
9 18 ::/0 On-link
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>route print -6 | find "::/0"
9 18 ::/0 On-link
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>route print -6 | find "::/0"
10 26 ::/0 fe80::5efe:10.120.58.150

C:\Users\John>

Under Windows XP or Server 2003, data flow in ISATAP will not be interruptted.
BUT, when disable IPv6 support in LAN NIC, ISATAP data flow's speed will
drop to 100kbyte/second. Enable IPv6 support will improve speed at once.

In all situation above, client pc NIC connect to LAN without native IPv6
access router. That's to say, all IPv6 data flow must be tunneled.