What are the differences between trunking and interface group?


Interface Group:
===============

An "interface group" is a collection of source addresses that share a
common subnet (also know as prefix). With the addition of this new
feature to Solaris 2.6, systems can have multiple physical interfaces 
on the same subnet.

With the addition of interface groups, the problem of inbound packets
arriving through multiple interfaces and outbound packets leaving
through one single interface has been addressed.

IP uses an interface group to rotate source address selection when the
source address is unspecified. In the case of multiple physical
interfaces in the same group, IP scatters traffic across different IP
addresses on a per-IP-destination basis.

Interface group provides load balancing but does not provide
automatic failover.

Other aspects of interface groups are:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Interface group works at the IP layer.

Interface group works across different type of NIC's and network
drivers.

Interface group support is part of the OS with Solaris 2.6 and above.
The same can be enabled by setting the ndd parameter
ip_enable_groups_ifs to 1.

The use of an interface group requires that the network interface cards 
have their own MAC addresses.

Interface group allows for multiple interfaces on a system to have IP
addresses belonging to the same subnet (but not the same IP address).

An interface group can be formed with different network interface types.
Interface types can be a mix of hme, le, qfe, etc.




Trunking:
========

Sun Trunking enables you to aggregate the collective bandwidth of the
links on Sun QuadFastEthernet cards and Sun GigabitEthernet cards.  Sun
Trunking  software provides the ability to aggregate up to eight 10/100
Mbps FastEthernet ports into a single virtual link.

Other aspects of trunking are: 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Trunking works at the MAC Layer.

Trunking enables load sharing across network interfaces.

Trunking requires a special software/driver (Sun Trunking 1.x)

Trunking requires special/specific NIC hardware (QFE, GE) in addition to
a Sun Trunking compatible switch.

Trunking enables multiple interfaces (up to 8) to carry the same IP
address.

Trunking between multiple interfaces requires the same NIC hardware type
and device driver.

Load balancing takes place based on the configured trunking
policy. The four supported trunking policies used in the Trunking
software are MAC (default), round robin (used mainly for server
back-to-back connections), IP destination address and IP source
address/IP destination address.

In the event of a link failure, Sun Trunking software automatically
redistributes the load across the remaining links.

Solaris 8 10/00 Update and onwards provides network adapter failure 
detection and outbound network packet load spreading. These are available 
with the base Solaris IP stack. This feature is called IP Network Multipathing.