I am having a problem with the IPv6 functionality on my W7 Ultimate x64 Eng. I am using an AVM Fritz!box 7390 as edge router that has a 6to4 tunnel configured to sixxs.net. The router is sending RAs announcing its global prefix 2a01:****:****:0:/64 w/ a lifetime of 7200 sec. My W7 PC is configuring two addresses (fixed and temporary) based on the prefix. So far everything works fine. Whenever the router loses the tunnel it invalidates the 2a01:.. prefix and publishes as new prefix an Unique Local Address (ULA) prefix fdd8:****:****:0/64. The invalidation is done by sending a RA with a lifetime of 0 for the public prefix and 7200 for the ULA prefix. After this the public addresses are marked as “Deprecated” and the ULA addresses as “Preferred”. Behavior is still ok until here. When the tunnel is up again at the router it is sending a new RA invalidating the ULA prefix and setting the global prefix lifetime back to 7200. And here things start to go wrong. W7 is setting the ULA addresses to “Deprecated” as required by the RA but it does not change the state of the global addresses back to “Preferred”. So I am ending w/ a system where all IPv6 addresses (except Link-Local) are “Deprecated”. And the addresses remain in this state ignoring the RAs from the router w/ the valid global prefix. The only work-around for this behavior I came up with was to disable and enable the respective network interface. This behavior has been observed on multiple W7 PCs using various Ethernet and Wi-Fi adapters. Linux systems do not suffer from this issue.

Hi Friend, the samething is happening here. do you got any answer?

In another forum a user reported that AVM has acknowledged that it is a bug in the Fritz!box firmware. It's supposed to get fixed w/ the next update.

In another forum a user reported that AVM has acknowledged that it is a bug in the Fritz!box firmware. It's supposed to get fixed w/ the next update. Can someone post a link to that other forum thread please.

Obviously it's not a bug in Fritz!box's firmware but AVM is only providing a workaround. The new lab version of the firmware for Fritz!box 7270 contains: "Internet: IPv6 - Workaround: Windows 7 akzeptiert bis zum Reboot nicht mehr den gleichen Prefix, wenn dieser einmalig invalidiert wurde." ("Until reboot Windows 7 does not accept the same prefix after it has been invalidated once.") And the workaround seems to be increasing the subnet nr to get IPv6 up again after a subnet has been deprecated. IMHO that's worse than the original bug if you have servers w/ static addresses. As I have a 7390 I am not able to test it myself until a lab version for this model is available.

Obviously it's not a bug in Fritz!box's firmware but AVM is only providing a workaround. The new lab version of the firmware for Fritz!box 7270 contains: "Internet: IPv6 - Workaround: Windows 7 akzeptiert bis zum Reboot nicht mehr den gleichen Prefix, wenn dieser einmalig invalidiert wurde." ("Until reboot Windows 7 does not accept the same prefix after it has been invalidated once.") And the workaround seems to be increasing the subnet nr to get IPv6 up again after a subnet has been deprecated. IMHO that's worse than the original bug if you have servers w/ static addresses. As I have a 7390 I am not able to test it myself until a lab version for this model is available. I also have a 7390. I did some more research and it appears that possibly it is AVM's fault. RFC 2462 does not discuss a provision for putting an address from deprecated back to preferred state. What does "subnet nr" mean by the way - I'm not familiar with the NR acronyn. Do you mean the subnet ID?

You're probably right. But this leads to the question how the Fritz!box should react if the IPv6 tunnel gets lost. Especially in the case of sixxs.net where the subnet prefix is not statically configured on the FB but dynamically loaded from sixxs.net when opening the tunnel. And the RFC does nowhere prohibit to reuse an address after it has been deprecated. But definitely the current situation is not very satisfying. As of today each time the FB gets rebooted or the tunnel gets closed I have to disable/enable the NICs of all machines. On the other hand as I stated above having a new subnet address each time is worse imho. Maybe a longer grace period until invalidating a prefix would mitigate most issues.

You're probably right. But this leads to the question how the Fritz!box should react if the IPv6 tunnel gets lost. Especially in the case of sixxs.net where the subnet prefix is not statically configured on the FB but dynamically loaded from sixxs.net when opening the tunnel. And the RFC does nowhere prohibit to reuse an address after it has been deprecated. But definitely the current situation is not very satisfying. As of today each time the FB gets rebooted or the tunnel gets closed I have to disable/enable the NICs of all machines. On the other hand as I stated above having a new subnet address each time is worse imho. Maybe a longer grace period until invalidating a prefix would mitigate most issues. I have just found a workaround if you are getting a relatively static prefix from the router. In my case, my ISP is native IPv6 so it's not a tunnel issue, but this should work anyway. Essentially it's assigning a static IP address, which doesn't seem to work from the Network adapter properties window. Here's the procedure: In a command prompt running as administrator, run netsh interface ipv6 global set randomizeidentifiers=disabled In the same command prompt, run netsh interface ipv6 set privacy state=disabled Reboot your PC to get a new IPv6 address Run netsh interface ipv6 show address Note the interface number for your LAN/WiFi interface Copy the IPv6 address listed for that interface to the clipboard Run netsh interface ipv6 set address interface=<your interface ID> address=<your Ipv6 address> validlifetime=infinite preferredlifetime=infinite store=persistent This survives a router Internet reconnection and also survives reboots.

AVM have an upcoming firmware version - 84.05.01 which removes this problem. I have a pre-release version of it running on my 7390, and the behaviour has now changed. When the PPP connection (or IPv6 tunnel) is dropped, the router no longer sends RA packets which invalidate the IPv6 prefix. I am unsure when this firmware will be released, but sit tight it should be soon!