How to report IPv6 bug to Microsoft - Vista and 7 won't "undeprecate" a prefix

Mark Smith msmith at
Thu Apr 7 08:04:36 CEST 2011


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".

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.)


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