HP-UX Reference (11i v2 04/09) - 1M System Administration Commands A-M (vol 3)

i
ifconfig(1M) ifconfig(1M)
IPv6 Interfaces
inet6 must be specified when an IPv6 interface is configured. The address for an IPv6 interface can either
be a hostname present in the host name database (see hosts(4)), or an address in the IPv6 colon notation.
Stateless Address Auto-configuration:
Unlike IPv4 interfaces, IPv6 interfaces can be configured without an address and/or a prefix. Stateless
address autoconfiguration requires no manual configuration of hosts, minimal (if any) configuration of
routers, and no additional servers. A primary interface
(lanX:0) is automatically assigned a link-local
address by the system when the interface is configured. A link-local address comprises the well-known
link-local prefix FE80::/10 and the interface identifier, which is typically 64 bits long and is based on
EUI-64 identifiers. The link-local address allows automatic discovery of other hosts and routers on the
same link, using the Neighbor Discovery Protocol (see NDP(7P)). The link-local address can be used as
the source address to communicate with other nodes when no routers are present. If a router on the local
link advertises prefixes in router advertisements, the host autoconfigures its secondary interfaces and its
default gateway. The address of an autoconfigured secondary interface is formed by prepending the
prefix received from the router to the interface identifier, the same interface identifier that is used in
forming the primary interface.
Manual Address Configuration:
IPv6 interfaces can also be configured with manually assigned addresses and/or prefixes. A primary
interface must be configured with a link-local address and the prefix must not be specified. The prefix is
always 10. The universal/local bit, the U bit, of the interface identifier must be 0, per section 2.5.1 of
RFC 2373. Accordingly, a manually assigned address for a primary interface must have the following
pattern: FE80::xMxx:xxxx:xxxx:xxxx where x is any hexadecimal digit, and M must be 0, 1, 4, 5, 8, 9, C,
or D.
When a primary interface is configured with a manually assigned address, secondary interfaces will be
autoconfigured if the host receives prefixes from router advertisements. The addresses on the secondary
interfaces will be derived from the interface identifier portion of manually configured address in the pri-
mary interface.
When a secondary interface is configured with a manually assigned address, and if the user chooses an IP
index number that has been used for an autoconfigured secondary interface, the manual configuration
overwrites the autoconfiguration. When this happens, network connectivity through the overwritten
autoconfigured IP address is temporarily lost. At a later time, when the host receives the next router
advertisement, the host will bring up another secondary interface with a different IP index number, but
with the same IP address, and network connectivity through that IP address is restored. Normally, a
user can avoid this by checking used IP index numbers. However, there is always a possibility that
address autoconfiguration due to router advertisement is happening concurrently while the user manu-
ally configures secondary interfaces.
To disable communication through a specific IP address on an autoconfigured secondary interface, that
secondary interface should be marked down, not removed or overwritten with a different IP address. If
that interface is removed or overwritten, the host will reconfigure another secondary interface with the
same IP address when it receives the next router advertisement. Alternatively, the router can be
configured to stop advertising the prefix that corresponds to the offending IP address.
IPv6 interface flags displayed:
An IPv6 interface may have three new flags that are not present in an IPv4 interface: TUNNEL, AUTO,
and ONLINK. The TUNNEL flag is set for the tunnel interfaces. The AUTO flag is set for autoconfigured
secondary interfaces. The ONLINK flag is set for interfaces with IP addresses that can be reached
without going through a router.
Examples:
Stateless address autoconfiguration with link-local address
ifconfig lan0 inet6 up
Manual configuration for a primary interface with link-local address
ifconfig lan0 inet6 fe80::1 up
Manual configuration for a secondary interface with link-local address
ifconfig lan0:1 inet6 fe80::3 up
Manual configuration for a secondary interface with global address
ifconfig lan0:3 inet6 2222::4 up
Section 1M−−302 Hewlett-Packard Company − 4 − HP-UX 11i Version 2: September 2004