Introduction to IPv6
IPv6 is a network layer protocol used in switching-packet networks. The main characteristic of IPv6 is the large amount of available addresses, as it uses 128 bits-long addresses instead of the 32 bits length provided by IPv4. It also simplifies the network management avoiding the use of complex subnetting schemes.
Some of the advantages provided by IPv6 are:
- IP security
- Mobile IP addresses
- Simplified header structure
- Address auto-configuration
- Anycast (one address out of many) and mandatory multicast addresses
Main Features of IPv6 in the Virtual Traffic Manager
The Virtual Traffic Manager provides the following aspects of IPv6 support:
- The Virtual Traffic Manager acts as a gateway for IPv6
- The Virtual Traffic Manager can process different IP address versions at your front end and back-end servers
- The Virtual Traffic Manager is able to work in IPv4-IPv6 mixed-networks, and in just-IPv4 networks
IPv6 unicast addresses can be used for configuring your Virtual Traffic Manager wherever IPv4 addresses can be used: in traffic IP addresses (excluding RHI and multi-hosted traffic IP addresses), when specifying nodes or the addresses a virtual server is listening on, in TrafficScript rules, and so on.
Your Virtual Traffic Manager can also function as a gateway from IPv4 to IPv6 or vice versa and even both at the same time.
Technical Restrictions
Some restrictions apply when using IPv6 in the Virtual Traffic Manager environment. Although they should not affect the normal running of the software, these restrictions must always be taken into account.
This is a list of the main restrictions regarding the use of IPv6:
- The internal communication between different Virtual Traffic Managers is done over the IPv4 protocol.
- Heartbeat messages only work on IPv4, as does the administration server.
- When using a hostname in the configuration of a back-end node, the Virtual Traffic Manager will first look up the IPv4 address. If you want to use the IPv6 address of a machine where the DNS has both IPv4 and IPv6 addresses, you must enter the IPv6 address directly.
- If a host has only an IPv6 address in the DNS, that address will be used.
Tuning Duplicate Address Detection
This section applies only to the Virtual Traffic Manager software variant. Virtual Traffic Manager hardware appliances, virtual appliances, and cloud variants are automatically configured with Duplicate Address Detection correctly tuned.
The Duplicate Address Detection (DAD) feature of many operating systems seeks to ensure that two machines do not raise the same address simultaneously. This feature can conflict with the Virtual Traffic Manager’s fault tolerance; when an IP is transferred from one Virtual Traffic Manager system to another, timing conditions may trigger DAD on the Virtual Traffic Manager that is raising the address. The DAD feature can be tuned as follows:
- Linux: the sysctls are called net.ipv6.conf.default.dad_transmits and net.ipv6.conf.all.dad_transmits. Add (or change) these lines in /etc/sysctl.conf to:
net.ipv6.conf.default.dad_transmits = 0and:
net.ipv6.conf.all.dad_transmits = 0For immediate change, issue this command for each relevant interface (eth1 in this example), plus “default” and “all”:
# sysctl -w net.ipv6.conf.eth1.dad_transmits=0
# sysctl -w net.ipv6.conf.default.dad_transmits=0
# sysctl -w net.ipv6.conf.all.dad_transmits=0