IPv6 stops working after a brief inactivity

[websitenet]

Hello!  After about 10 minutes of inactivity, the Internet can no longer communicate with my server's IPv6 IP address, and I'm not sure why.

When I set up the tunnel broker using CentOS 6.2 and the sit0/sit1 method, and do a "/etc/init.d/network restart", everything comes up beautifully.  I can ping out and connect to IPv6 hosts, and hosts can do the same inbound to me.

After about 10 minutes of inactivity, hosts can no longer ping inbound, and can no longer access other inbound resources like ssh and http.  It's as if the tunnel is down.

On the server though, if I ping outbound IPv6 to anywhere, it brings the tunnel back to life and the world can ping and access inbound services.

I heard that IPv6 relies on icmp to determine if an IP is online, so I ensured icmpv6 is enabled inbound:
iptables -I INPUT -p icmpv6 -j ACCEPT

Still no help.  The problem temporarilly goes away if I log in the to the server and do a
ping6 ipv6.any-host-on-the-internet

Then other hosts will see my IPv6 address as up, at least for a few minutes.

Anyone have any ideas?  I'd rather not set up a cron to do an icmp ipv6 ping outbound every minute, unless it's a last resort, but I'd rather fix the problem than just apply some duct tape to it.

Below are my configs.  For security reasons, I changed some of the below ipv4 and ipv6 addresses, so these IPs are not the actual ones i'm working with.

/etc/sysconfig/network:

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NETWORKING=yes
HOSTNAME=my.host.com
GATEWAY=209.100.1.1
NETWORKING_IPV6=yes
IPV6_AUTOTUNNEL=yes
IPV6FORWARDING=yes
IPV6_AUTOCONF=no


/etc/sysconfig/network-scripts/ifcfg-eth0:

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DEVICE=eth0
BOOTPROTO=static
BROADCAST=209.100.1.7
GATEWAY=209.100.1.1
HWADDR=00:25:90:56:10:35
IPADDR=209.100.1.2
IPV6INIT=yes
IPV6_AUTOCONF=no
NETMASK=255.255.255.248
NM_CONTROLLED=no
ONBOOT=yes


/etc/sysconfig/network-scripts/ifcfg-sit1:

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TYPE=sit
DEVICETYPE=sit
ONBOOT=yes
DEVICE=sit1
BOOTPROTO=none
IPV6INIT=yes
IPV6ADDR=2001:470:1f:d2::2/64
IPV6TUNNELIPV4=216.218.224.42
IPV6TUNNELIPV4LOCAL=209.100.1.2
IPV6ADDR_SECONDARIES="2001:470:1f:d2:4e66:84d4:d1d7:fd38/64"


/etc/sysconfig/network-scripts/route6-sit1:

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::/0 dev sit1

Output of "ifconfig -a":

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eth0      Link encap:Ethernet  HWaddr 00:25:90:56:10:35
         inet addr:209.100.1.2  Bcast:209.100.1.7  Mask:255.255.255.248
         inet6 addr: fe80::225:90ff:fe56:1035/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:138398008 errors:0 dropped:0 overruns:0 frame:0
         TX packets:213651810 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:65616826953 (61.1 GiB)  TX bytes:295239216577 (274.9 GiB)
         Interrupt:16 Memory:fba00000-fba20000

eth0:1_3 Link encap:Ethernet  HWaddr 00:25:90:56:10:35
         inet addr:209.100.1.3  Bcast:209.100.1.7  Mask:255.255.255.248
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         Interrupt:16 Memory:fba00000-fba20000

eth1      Link encap:Ethernet  HWaddr 00:25:90:56:10:36  
         BROADCAST MULTICAST  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
         Interrupt:18 Memory:fb900000-fb920000

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:10915 errors:0 dropped:0 overruns:0 frame:0
         TX packets:10915 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:100624590 (95.9 MiB)  TX bytes:100624590 (95.9 MiB)

sit0      Link encap:IPv6-in-IPv4  
         inet6 addr: ::127.0.0.1/96 Scope:Unknown
         inet6 addr: ::209.100.1.2/96 Scope:Compat
         inet6 addr: ::209.100.1.3/96 Scope:Compat
         UP RUNNING NOARP  MTU:1480  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:5 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

sit1      Link encap:IPv6-in-IPv4  
         inet6 addr: 2001:470:1f:d2:4e66:84d4:d1d7:fd38/64 Scope:Global
         inet6 addr: 2001:470:1f:d2::2/64 Scope:Global
         inet6 addr: fe80::d169:f202/128 Scope:Link
         UP POINTOPOINT RUNNING NOARP  MTU:1480  Metric:1
         RX packets:18 errors:0 dropped:0 overruns:0 frame:0
         TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:1872 (1.8 KiB)  TX bytes:1872 (1.8 KiB)


And output of "ip -6 route" does show default route over device sit1:

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2001:470:1f:d2::/64 via :: dev sit1  proto kernel  metric 256  mtu 1480 advmss 1420 hoplimit 4294967295
default dev sit1  metric 1024  mtu 1480 advmss 1420 hoplimit 4294967295

[shogsbro]

Most likely your providers router does not provide a fully working inbound mapping of IP protocol 41 (6to4). I've got the exact same problem, only the Thomson TG587n V2 provided by my ISP (O2 Broadband) times out after a 1 minute.