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If you're preparing to roll out IPv6 on your network, this concise book provides the essentials you need to support this protocol with DNS. You'll. This article presents a tutorial on building an IPv6 DNS Linux server that provides . An essential step before installing the IPv6 compliant BIND version is to. Download here Read DNS and BIND on IPv6 Ebook Read online and read pdf by Cricket Liu, Ebook Reader Read DNS and BIND on IPv6.
The fragmentation extension header is used. Host table A configurable table that associates an Internet address with a host name for example, This table is used by the sockets name resolver, either before a DNS lookup or after a DNS lookup fails determined by host name search priority.
Sometimes referred to as a logical interface.
DNS and BIND, 5th Edition
Basic error types remain, such as destination unreachable, echo request and reply. New types and codes are added to support neighbor discovery and related functions. IP header Variable length of bytes, depending on IP options present. Fixed length of 40 bytes. There are no IP header options. Generally, the IPv6 header is simpler than the IPv4 header. IP header options Various options might accompany an IP header before any transport header.
The IPv6 header has no options. Instead, IPv6 adds additional optional extension headers. Currently, IPv6 supports some extension headers.
The type of header immediately following the IPv6 header. Uses the same values as the IPv4 protocol field.
But the architectural effect is to allow a currently defined range of next headers, and is easily extended. The next header will be a transport header, an extension header, or ICMPv6. Uses different codes to designate an IPv6 traffic class. Many types exist; for example, Ethernet. Bind should be configured as cache-only name server, with recursive look-up. This is because it is irrelevant to be authoritative in a lab envirorment. The named. The first one for IPv4 and the second one for IPv6.
They are named iptables and ip6tables. In any case, for a lab test, both services can be stopped as shown in Figure For debugging purposes it is better to launch it in debug mode and in foreground mode as shown in Figure Once bind is started it can be tested by using the dig tool. If it works, then the DNS server is ready. Therefore, if command tools like dig or dnslookup are used, the system will automatically use this DNS.
Take a look at Figure The host is unable to use this data. The reason is that the default setting on the dig tool is IPv4 also in an only IPv6 only envirorment. It is likely that this behavior will change in the next releases. This is because of the absence of an AAAA record in itesys. This prefix is named well-know prefix and is not a globally routable prefix. With this latest test we can be sure that the DNS64 server is working well. Notice that the nslookup tool normally uses IPv4 as default also in IPv6 only.
Useful when you have zone files. Here it is a caching only nameserver so it is irrelevant; 2 In case the domain referenced in the query does not exist, bind marks the answer with the non-authoritative flag. This is irrelevant in a lab envirorment; 3 Bind listens to all available interfaces.
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There is no reason to put limits in a lab envirorment; 5 This is the DNS64 configuration. As seen before with the query answer for www. If the gateway is configured with NAT64 it will detect this special address translating it to the original IPv4 address. Both sender and destination IPv4 addresses will be translated by NAT64 in accordance with its configuration.
In any case they are enabled by default. This is the most elementary NAT64 configuration. It can be tried on a Cisco series too. It only depends on IOS release. DNS64 is useless if used alone. At the time of writing this document, CEF has to be disabled to make the system work.
Another restriction is that ALG support is not provided for many protocols.
How much of a restriction this really is may be questionable, because many protocols are not programmed with NAT in mind, and in any case, with any technology, there will be some restrictions for customers if NAT is used.
With 2 IPv6 routing is enabled. Row 5 is very important because it is related to the translation of the destination IPv6 addresses. The well-know prefix is configured in the DNS64 server that generates this 34 kind of destination address. Therefore if multiple versions of the same application are available, the local users have difficulty selecting the right version supporting the exact IP version required.
Informational [Page 6] RFC Application Aspects of IPv6 Transition March To avoid problems with one application not supporting the specified protocol version, it is desirable to have hybrid applications supporting both. This application would perform connection establishment or similar tasks and pass the opened socket to another application.
However, as applications such as this would have to do more than just perform a DNS lookup or determine the literal IP address given, they will become complex -- likely much more so than a hybrid application. Furthermore, writing "wrapping" applications that perform complex operations with IP addresses such as FTP clients might be even more challenging or even impossible.
In short, wrapper applications do not look like a robust approach for application transition. However, upgrading every node to IPv6 at the same time is not feasible, and transition from IPv4 to IPv6 will be a gradual process.
DNS and BIND on IPv6 (pdf)
Dual-stack nodes provide one solution to maintaining IPv4 compatibility in unicast communications. In this section we will analyze different application transition scenarios as introduced in section 2 and guidelines for maintaining interoperability between applications running in different types of nodes.
Note that the first two cases, IPv4-only and IPv6-only applications, are not interesting in the longer term; only few applications are inherently IPv4- or IPv6-specific, and should work with both protocols without having to care about which one is being used.
To allow an application to communicate with other nodes using IPv6, the first priority is to port applications to IPv6. We strongly recommend that application developers not use these mechanisms when application source code is available.
Also, they should not be used as an excuse not to port software or to delay porting. These mechanisms provide IPv4 temporary addresses to the applications and locally make a translation between IPv4 and IPv6 communication. Therefore, these IPv4 temporary addresses are only valid in the node scope.
This way the application will be IPv6-only. This IPv6-only source code cannot work in IPv4-only nodes, so the old IPv4 application should be maintained in these nodes.
This necessitates having two similar applications working with different protocol versions, depending on the node they are running e. This case is undesirable, as maintaining two versions of the same source code per application could be difficult. This approach would also cause problems for users having to select which version of the application to use, as described in section 3. In these dual-stack nodes, this default behavior allows a limited amount of IPv4 communication using the IPv4-mapped IPv6 addresses.
IPv6-only server: When an IPv4 client application sends data to an IPv6-only server application running on a dual-stack node by using the wildcard address, the IPv4 client address is interpreted as the IPv4-mapped IPv6 address in the dual-stack node.
This allows the IPv6 application to manage the communication. However, IPv4 packets will be exchanged between the nodes. If it Shin, Ed. However, IPv4 packets will be exchanged between applications. This option could be useful if applications use new IPv6 features such as Flow Label.
In these cases, there are two ways to handle the problem: 1. Deploy two different versions of the application possibly attached with '6' in the name. Deploy just one application supporting both protocol versions as described in the next section. The first method is not recommended because of a significant number of problems associated with selecting the right applications.
These problems are described in sections 3. Therefore, there are two distinct cases to consider when writing one application to support both protocols: 1.
Whether the application can or should support both IPv4 and IPv6 through IPv4-mapped IPv6 addresses or the applications should support both explicitly see section 4. Whether the systems in which the applications are used support IPv6 see section 4.
Note that some systems will disable by default support for internal IPv4-mapped IPv6 addresses. The security concerns regarding these are legitimate, but disabling them internally breaks one transition mechanism for server applications originally written to bind and listen to a single socket by using a wildcard address. This forces the software developer to rewrite the daemon to create two separate sockets, one for IPv4 only and the other for IPv6 only, and then to use select.
However, mapping-enabling of IPv4 addresses on any particular system is controlled by the OS owner and not necessarily Shin, Ed. This complicates developers' work, as they now have to rewrite the daemon network code to handle both environments, even for the same OS.
Over time, the existing IPv4-only applications could be removed. As we have only one version of each application, the source code will typically be easy to maintain and to modify, and there are no problems managing which application to select for which communication.
This transition case is the most advisable. During the IPv6 transition period, applications supporting both IPv4 and IPv6 should be able to communicate with other applications, irrespective of the version of the protocol stack or the application in the node. Dual applications allow more interoperability between heterogeneous applications and nodes.
If the source code is written in a protocol-independent way, without dependencies on either IPv4 or IPv6, applications will be able to communicate with any combination of applications and types of nodes.
Implementations typically prefer IPv6 by default if the remote node and application support it. However, if IPv6 connections fail, version-independent applications will automatically try IPv4 ones. The resolver returns a list of valid addresses for the remote node, and applications can iterate through all of them until connection succeeds.
Application writers should be aware of this protocol ordering, which is typically the default, but the applications themselves usually need not be [ RFC ]. If the source code is written in a protocol-dependent way, the application will support IPv4 and IPv6 explicitly by using two separate sockets.
Note that there are some differences in bind implementation - that is, in whether one can first bind to IPv6 wildcard addresses, and then to those for IPv4. Writing applications that cope with this can be a pain.
A more detailed porting guideline is described in section 6. This would typically be done to avoid supporting two application versions for older and newer operating systems, or to support a case in which the user wants to disable IPv6 for some reason.
The most important case is the application support on systems where IPv6 support can be dynamically enabled or disabled by the users.
DNS and BIND on IPv6 (pdf)
Applications on such a system should be able to handle a situation IPv6 would not be enabled. Another scenario is when an application is deployed on older systems that do not support IPv6 at all even the basic APIs such as getaddrinfo. In this case, the application designer has to make a case-by-case judgment call as to whether it makes sense to have compile-time toggle between an older and a newer API having to support both in the code , or whether to provide getaddrinfo etc. The application will need to handle this case or build the loop so that errors are ignored until the last address family.
Applications have been developed with IPv4 network protocol in mind. This assumption has resulted in many IP dependencies through source code. The following list summarizes the more common IP version dependencies in applications: Shin, Ed.
The following subsections describe the problems with the aforementioned IP version dependencies. Although application source code can be ported to IPv6 with minimum changes related to IP addresses, some recommendations are given to modify the source code in a protocol-independent way, which will allow applications to work with both IPv4 and IPv6.
Presentation Format for an IP Address Many applications use IP addresses to identify network nodes and to establish connections to destination addresses. This IP address is usually provided in the presentation format, as a string. There are two problems when porting the presentation format for an IP address: the allocated memory and the management of the presentation format.
Usually, the memory allocated to contain an IPv4 address representation as a string is unable to contain an IPv6 address. Applications should be modified to prevent buffer overflows made possible by the larger IPv6 address. IPv4 and IPv6 do not use the same presentation format. IPv4 uses a dot. In cases where one must be able to specify, for example, port numbers with the address see below , it may be desirable to require placing the address inside the square brackets [ TextRep ].
With IPv4 these are often coupled with a colon; for example, " However, this approach would be ambiguous with IPv6, as colons are already used to structure the address.Avoiding a Bogus Nameserver Managing delegation with stubs 9. Therefore, there are two distinct cases to consider when writing one application to support both protocols: 1.
Top-Level Domains E. Limiting SOA queries To provide resilience in the event of computer or network failure, multiple DNS servers are usually provided for coverage of each domain. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Generally, the IPv6 header is simpler than the IPv4 header. Data Format A.