Knowledge Base ISC Main Website Ask a Question/Contact ISC
IPv6 Changes in BIND 9.11.0, BIND 9.10.4 and BIND 9.9.9.
Author: Mark Andrews Reference Number: AA-01349 Views: 9558 Created: 2016-02-22 04:44 Last Updated: 2018-04-20 23:13 0 Rating/ Voters

BIND 9.11.0, BIND 9.10.4 and BIND 9.9.9 introduces two IPv6 related changes.

  • The first change is to the preferred-glue option.  Preferred-glue now defaults to the transport that the query was received over.  If named receives a query over IPv6 and there is not enough space to add both A and AAAA records to the additional section then named will add AAAA records in preference to A records.  The reverse is true for queries received over IPv4 where A is preferred over AAAA. The impact of this is that as IPv6-only recursive servers start to appear they will get the AAAA records they need to make further lookups without having to explicitly query for them.  Legacy IPv4-only servers will also get the A records they need.
  • The second change is to BIND 9.11.0 only, and is to add a small bias to the next server to query selection algorithm to prefer IPv6 servers over IPv4 servers provided they are still reasonably close based on the measured response times.  The amount of bias can be controlled by setting v6-bias and it defaults to 50 ms. This will have the effect of moving most queries for zones with both IPv4 and IPv6 servers to the IPv6 servers when the recursive server is dual stacked provided the IPv4 and IPv6 paths have roughly the same delay. 

Both of these changes combined should help sites see when they can stop supporting IPv4 as a transport by reducing the reliance on IPv4.  While that is still years away for many, we need to support the transition now as nameservers are often not upgraded for years. 

© 2001-2018 Internet Systems Consortium

For assistance with problems and questions for which you have not been able to find an answer in our Knowledge Base, we recommend searching our community mailing list archives and/or posting your question there (you will need to register there first for your posts to be accepted). The bind-users and the dhcp-users lists particularly have a long-standing and active membership.

ISC relies on the financial support of the community to fund the development of its open source software products. If you would like to support future product evolution and maintenance as well having peace of mind knowing that our team of experts are poised to provide you with individual technical assistance whenever you call upon them, then please consider our Professional Subscription Support services - details can be found on our main website.

Custom Fields
  • CHANGES reference: 4201, 4222
  • There is no feedback for this article
Quick Jump Menu