Specifications

Chapter 6. IBM Virtual Fabric 10Gb Switch Module implementation 265
6.4.2 Ports and trunking
When using port trunk groups between two switches, you can create a virtual link between
the switches, operating with combined throughput levels that depend on how many physical
ports are included.
Two trunk types are available:
Static trunk groups (portchannel), and dynamic LACP
trunk groups
.
Up to 18 trunks of each type are supported in stand-alone (non-stacking) mode, and 64
trunks of each type are supported in stacking mode, depending of the number and type of
available ports. Each trunk can include up to eight member ports.
Trunk groups are also useful for connecting a VFSM to third-party devices that support link
aggregation, such as Cisco routers and switches with EtherChannel technology (not ISL
trunking technology) and the Sun Quad Fast Ethernet Adapter. Trunk group technology is
compatible with these devices when they are configured manually.
Trunk traffic is statistically distributed among the ports in a trunk group, based on various
configurable options.
Also, because each trunk group is composed of multiple physical links, the trunk group is
inherently fault tolerant. If one connection between the switches is available, the trunk
remains active, and statistical load balancing is maintained whenever a port in a trunk group
is lost or returned to service.
Static trunk group configuration rules
The trunking feature operates according to specific configuration rules. When creating trunks,
consider the following rules that determine how a trunk group reacts in any network topology:
򐂰 All trunks must originate from one network entity (a single device, or multiple devices that
act in a stack) and lead to one destination entity. For example, you cannot combine links
from two different servers into one trunk group.
򐂰 Ports from different member switches in the same stack (see 6.2, “Stacking” on page 240)
may be aggregated together in one trunk.
򐂰 Any physical switch port can belong to only one trunk group.
򐂰 Depending on port availability, the switch supports up to eight ports in each trunk group.
򐂰 Internal (INTx) and external ports (EXTx) cannot become members of the same
trunk group.
򐂰 Trunking from third-party devices must comply with Cisco EtherChannel technology.
򐂰 All trunk member ports must be assigned to the same VLAN configuration before the trunk
can be enabled.
򐂰 If you change the VLAN settings of any trunk member, you cannot apply the change until
you change the VLAN settings of all trunk members.
򐂰 When an active port is configured in a trunk, the port becomes a trunk member when you
enable the trunk by running /cfg/l2/trunk <x>/ena. The Spanning Tree parameters for
the port then change to reflect the new trunk settings.
򐂰 All trunk members must be in the same Spanning Tree Group (STG) and can belong to
only one STG. However if all ports are tagged, then all trunk ports can belong to
multiple STGs.
򐂰 If you change the Spanning Tree participation of any trunk member to enabled or disabled,
the Spanning Tree participation of all members of that trunk changes similarly.