msmith at internode
Apr 7, 2011, 12:50 AM
Post #6 of 18
Re: How to report IPv6 bug to Microsoft - Vista and 7 won't "undeprecate" a prefix
[In reply to]
On 7/04/2011 4:23 PM, Ole Troan wrote:
>> A number of our customers are having trouble with IPv6 under Windows Vista and 7 on our IPv6 trial.
>> Currently we are giving customers a static delegated prefix via DHCPv6-PD (a /60 currently). When they have an ADSL drop out, some IPv6 CPE is deprecating the assigned LAN interface global /64 prefix by sending an RA with a zero second preferred lifetime for the prefix. Windows Vista and 7 are quite correctly labelling the prefix as deprecated, as it still has a non-zero valid lifetime. Deprecating the prefix at this time makes sense as there is a possibility that the delegated prefix may not be re-assigned to the CPE after the ADSL link is restored, and may be re-assigned by the ISP to another customer. This is also the behavior specified in the recently published RFC6204, "Basic Requirements for IPv6 Customer Edge Routers".
> no, it isn't.
> this behaviour breaks local communication within the home.
Hmm. Well that's the behavior this CPE seems to be exhibiting. I think
I've been fooled a bit by misremembering this clause from the RFC -
L-13: If the delegated prefix changes, i.e., the current prefix is
replaced with a new prefix without any overlapping time
period, then the IPv6 CE router MUST immediately advertise the
old prefix with a Preferred Lifetime of zero and a Valid
Lifetime of the lower of the current Valid Lifetime and 2
hours (which must be decremented in real time) in a Router
Advertisement message as described in Section 5.5.3, (e) of
However, I don't think that means that Vista and Windows 7 doesn't have
a bug though. Surely it is valid for a prefix to be "undeprecated"?
>> When the ADSL link comes up again, and the CPE re-acquires the same delegated prefix, it re-announces the same /64 onto the LAN with a non-zero preferred lifetime. Windows Vista and 7 receive and update the non-zero prefix lifetimes for the addresses, but do not change the addresses back to preferred. Windows XP does, as do other operating systems. Windows Vista and 7 not setting the addresses back to preferred seems to then cause IPv6 connectivity to then fail, causing Vista and 7 to revert back to using IPv4 only. Windows Vista and 7 have no trouble at this time with new prefixes, so the issue seems to be specifically related to changing a previously deprecated prefix back to a preferred one.
>> Does anybody know how I can report this bug with Microsoft on behalf of our customers?
>> (If anybody wants to have a go reproducing this, the latest CVS version of radvd now has a "DeprecatePrefix" option for prefixes. To view the IPv6 address status and lifetimes under Windows, use the "netsh interface ipv6 show address" "cmd" command.)