BIND 9.8.0 Adds DNS64 Support - Part 1 - What is DNS64?

The Internet Systems Consortium (ISC) recently introduced BIND 9.8.0, a major release with several new features. I'd like to focus on DNS64 support, which is an IPv4-IPv6 co-existence feature that enables IPv6 hosts to connect to IPv4 destinations via a NAT64 (IPv6-to-IPv4 network address translator). DNS64 functions operate on a recursive server which attempts to resolve queries on behalf of its clients.

When a client issues a query for a AAAA (IPv6 address) record type for a particular destination host, the DNS server initially behaves normally, locating the authoritative server and issuing the query. If AAAA record(s) are returned, the servers passes this to the resolver client and a native IPv6 connection ensues. If no AAAA records are received, the DNS64 service performs an additional query for the same destination host though for the A (IPv4 address) record type. If a successful response is received, the DNS64 service concatenates the returned IPv4 address to a pre-defined IPv6 prefix to formulate an IPv6 address. This IPv6 address is returned as the answer to the original AAAA query from the resolver client, and it connects the client to the NAT64 gateway.

The NAT64 gateway is configured to listen for IPv6 packets on all addresses within the same pre-defined IPv6 prefix that the DNS64 service uses to append resolved IPv4 addresses. When the client host sends the IPv6 packet to initiate the connection to the resolved IPv6 address, the NAT64 gateway receives the packet and it knows to what IPv4 destination it is destined as appended. Hence the NAT64 device allocates an outgoing source IPv4 address and initiates a connection to the IPv4 destination. The NAT64 device interconnects the IPv6 session with the originating host with the IPv4 session to the destination host. Thus IPv6 hosts are able to communicate with IPv4 destinations! For more details including a timeflow diagram please see my recent white paper which includes discussion of DNS64.

Comments

Post a Comment

Popular posts from this blog

Handy AAAA filter in BIND 9.8

The ISC introduced a pair of new configuration file options in BIND 9.8 to enable administrators to easily filter who may receive AAAA record type responses even if valid responses exist. For example, clients on subnets that do not have IPv6 network access can be excluded from receiving affirmative answers for AAAA queries. This feature provides simpler administration than the alternative mechanism using views. The first option, filter-aaaa-on-v4,defines whether the server will return AAAA records to certain clients. Such clients are defined by the address match list parameter of the second option, filter-aaaa. Note that BIND must be compiled with the --enable-filter-aaaa option on the configure command line to enable AAAA filtering. The syntax of these options is as follows: filter-aaaa-on-v4 (yes | no | break-dnssec) ; filter-aaaa {addr_match_list;} ; The filter-aaaa option identifies the address match list for which the filter-aaaa-on-v4 option is to be applied as described ...
Read more

Inglorious DDI

We all know how critical DHCP/DNS/IPAM (DDI) services are. Your network cannot function without them. But like most foundational elements of anything, they are certainly not glamorous...like good luck finding a home designer who specializes in home foundations. I would not be shocked should HGTV pass on my brilliant concept for a foundation building show. I suppose most people would find a show detailing footing depths and concrete pouring techniques rather boring.  Nevertheless, there are countless shows for redesigning and remodeling homes. On most episodes the foundation is out of sight, out of mind. If it's stable, no one wants to pay it attention, they just expect it to keep doing its job, supporting the structure. Once in a while a foundational issue is brought up that unexpectedly threatens to raise the budget to heighten the drama. All work stops until the issue is addressed. And you'll notice that the owner never denies paying the extra amount to fix the issue. ...
Read more

BIND 9.8.0 Adds DNS64 Support - Part 2 - How is it configured?

BIND 9.8.0 introduced a new dns64 option statement that can be configured within the server named.conf options block or within a view options block. Recall from a prior post that DNS64 configures a recursive DNS server to issue A record queries on behalf of a client requesting AAAA records, then appends the returned IPv4 address to a defined IPv6 prefix. This manufactured IPv6 address enables the querying host to connect to a NAT64 gateway which will terminate the IPv6 connection from the client and map it to an outbound IPv4 connection to the appended IPv4 address, completing the connection! Whew! BIND offers a number of useful parameters within the dns64 statement to control this process. The statement syntax is: dns64 IPv6_prefix { [clients {address_match_list };] [mapped {address_match_list };] [exclude {address_match_list };] [suffix IPv6_addr;] [recursive-only (yes|no);] [break-dnssec (yes|no);] }; The IPv6_prefix parameter is the prefix to which returned...
Read more