Technical data

4. Packages
Such a reduction is only allowed once to avoid ambiguities. The address 2001:0:0:1:2:0:0:3
can thus either be shortened to 2001::1:2:0:0:3 or 2001:0:0:1:2::3 but not to 2001::1:2::3
because then it would be unclear how the four zeros belong to the contracted regions.
Another ambiguity exists when an IPv6 address is to be combined with a port (TCP or UDP):
In this case you can not add the port immediately followed by a colon and value because the
colon is already used within the address and it is therefore unclear in some cases whether the
port specification is perhaps an address component. In such cases the IPv6 address is enclosed
in square brackets. This is the syntax also required in URLs (for example if a numerical IPv6
address should be used in the web browser).
Example 3: [2001:db8:900:551::2]:1234
Without the use of braces the following address is created 2001:db8:900:551::2:1234,
which without shortening equals to the address 2001:db8:900:551:0:0:2:1234 and thus has
no port appendend.
4.12.3. Configuration
General Settings
The general settings include at first the activation of IPv6 support and then the optional
assignment of an IPv6 address to the router.
OPT_IPV6 Activates IPv6 support.
Default setting: OPT_IPV6='no'
HOSTNAME_IP6 (optional) This variable sets the IPv6-address of the routers explicitely. If
the variable is not set the IPv6-address will be set to the first configured IPv6-subnet
(IPV6_NET_x, see below).
Example: HOSTNAME_IP6='IPV6_NET_1_IPADDR'
Subnet Configuration
This section describes the configuration of one or more IPv6 subnets. An IPv6 subnet is an
IPv6 address space specified by a so-called prefix and is bound to a certain network interface.
Further settings include the announcing of the prefix and of the DNS service within the subnet
and optional a router name within that subnet.
IPV6_NET_N This variable contains the number of used IPv6 subnets. At least one IPv6
subnet should be defined in order to use IPv6 in the local network.
Default setting: IPV6_NET_N='0'
IPV6_NET_x This variable contains the IPv6 address of the router and the size of the network
mask in CIDR notation for a specific IPv6 subnet. If the subnet is to be routed publicly
it usually is obtained from the Internet or tunnel provider.
Important: If the stateless auto-configuration should be activated in the subnet then the
length of the subnet prefix has to be 64 bits! (see the section on IPV6_NET_x_ADVERTISE
below)
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