© Copyright IBM Corp. 2011 285
Chapter 23. Basic Redundancy
IBM Networking OS 6.8 includes various features for providing basic link or device
redundancy:
•
“Trunking for Link Redundancy” on page 285
•
“Virtual Link Aggregation” on page 285
•
“Hot Links” on page 286
•
“Active MultiPath Protocol” on page 288
•
“Stacking for High Availability Topologies” on page 291
Trunking for Link Redundancy
Multiple switch ports can be combined together to form robust, high-bandwidth
trunks to other devices. Since trunks are comprised of multiple physical links, the
trunk group is inherently fault tolerant. As long as one connection between the
switches is available, the trunk remains active.
In Figure 34, four ports are trunked together between the switch and the enterprise
routing device. Connectivity is maintained as long as one of the links remain active.
The links to the server are also trunked, allowing the secondary NIC to take over in
the event that the primary NIC link fails.
Figure 34. Trunking Ports for Link Redundancy
For more information on trunking, see “Ports and Trunking” on page 107.
Virtual Link Aggregation
Using the VLAG feature, switches can be paired as VLAG peers. The peer switches
appear to the connecting device as a single virtual entity for the purpose of
establishing a multi-port trunk. The VLAG-capable switches synchronize their
logical view of the access layer port structure and internally prevent implicit loops.
The VLAG topology also responds more quickly to link failure and does not result in
unnecessary MAC flooding.
VLAGs are useful in multi-layer environments for both uplink and downlink
redundancy to any regular LAG-capable device. They can also be used in for
active-active VRRP connections.
For more information on VLAGs, see “Virtual Link Aggregation Groups” on
page 159.
Trunk Trunk
Server
NIC 1
NIC 2
Internet
Enterprise
Routing Switch
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