IPv4LL in SUSE Linux
====================

IPv4LL provides support of peer to peer address assignment from a
special link local IP range.

SUSE Linux contains three implementations of IPv4LL autoip protocol:


avahi-autoipd from avahi-autoipd package from avahi project
===========================================================

This is a daemon, that runs and assign IPv4LL address, either as a
fallback or at any time, depending on System/Zeroconf
AVAHI_AUTOIPD_FORCE_BIND sysconfig key (disabled by default).

The daemon runs permanently for each device, monitors the network
status, and assigns IPv4LL address when requested.

See http://avahi.org/wiki/AvahiAutoipd#ModesofOperation for more.


Activate avahi-autoipd implementation
-------------------------------------

- Install avahi-autoip package and check that System/Zeroconf
  AVAHI_AUTOIPD_FORCE_BIND sysconfig key is "yes" (the default).

- Set the address settings in the YaST network configuration either to
  None (to have IPv4LL address only) or DHCP (if you want DHCP together
  with IPv4LL).

- Note that NetworkManager uses avahi-autoipd by default.


For AVAHI_AUTOIPD_FORCE_BIND=false:
-----------------------------------

In this mode the daemon assigns IPv4LL address only of DHCP fails.

Advantage:
- All programs work with this setup.

Disadvantage:
- When DHCP assigns address, all existing IPv4LL connections are lost.


For AVAHI_AUTOIPD_FORCE_BIND=true:
----------------------------------

In this mode the deamon forces binding address from IPv4LL address, even if
standard IPv4 address exists.

Advantage:
- You can depend on IPv4LL address always assigned.

Disadvantage:
- Some programs don't work well with labeled IP addresses or interface
  aliases.



autoip from sysconfig package
=============================

autoip is not bound to sysconfig scripts and it is not called during
as sysconfig is using an own implementation. To enable you have to
set AVAHI_AUTOIPD_ENABLE=yes in /etc/sysconfig/avahi. Note, that it
starts unconditionally then and breaks bridges,vlan,bond, ...

If DHCP adrress is assigned, autoip ends immediately. Only if no DHCP
address is assigned, it stays running as a daemon and provides IPv4LL
address.


Activate autoip implementation
------------------------------

- Do not install avahi-autoipd package or set System/Zeroconf
  AVAHI_AUTOIPD_FORCE_BIND sysconfig key to "no".

- Set Zeroconf the address settings in the YaST network configuration.



IPv4LL assigned by dhcpcd
=========================

If dhcpcd fails to obtain a lease, it will probe for a valid IPv4LL
address. Once obtained it will probe every 10 seconds for a DHCP server.


Activate dhcpcd implementation
------------------------------

This implementation is not supported in SUSE yet. Enabling this
implementation would require several manual changes in the
/sbin/ifup-dhcp script (removal of -L argument, and skipping of calls to
${SCRIPTNAME}-autoip in /sbin/ifup (e. g. by not setting Zeroconf in the
YaST network configuration).