Chapter 24. Layer 2 Failover; Monitoring Trunk Links; Setting The Failover Limit - IBM RackSwitch G8000 Application Manual

Chapter 24. Layer 2 Failover

Monitoring Trunk Links

Setting the Failover Limit

© Copyright IBM Corp. 2011
The primary application for Layer 2 Failover is to support Network Adapter Teaming.
With Network Adapter Teaming, all the NICs on each server share the same IP
address, and are configured into a team. One NIC is the primary link, and the other
is a standby link. For more details, refer to the documentation for your Ethernet
adapter.
Note: Only two links per server can be used for Layer 2 Trunk Failover (one
primary and one backup). Network Adapter Teaming allows only one backup
NIC for each server blade.
Layer 2 Failover can be enabled on any trunk group in the G8000, including LACP
trunks. Trunks can be added to failover trigger groups. Then, if some specified
number of monitor links fail, the switch disables all the control ports in the switch.
When the control ports are disabled, it causes the NIC team on the affected servers
to failover from the primary to the backup NIC. This process is called a failover
event.
When the appropriate number of links in a monitor group return to service, the
switch enables the control ports. This causes the NIC team on the affected servers
to fail back to the primary switch (unless Auto-Fallback is disabled on the NIC team).
The backup switch processes traffic until the primary switch's control links come up,
which can take up to five seconds.
Figure 37 is a simple example of Layer 2 Failover. One G8000 is the primary, and
the other is used as a backup. In this example, all ports on the primary switch belong
to a single trunk group, with Layer 2 Failover enabled, and Failover Limit set to 2. If
two or fewer links in trigger 1 remain active, the switch temporarily disables all
control ports. This action causes a failover event on Server 1 and Server 2.
Figure 37. Basic Layer 2 Failover
Enterprise
Routing Switches
Internet
The failover limit lets you specify the minimum number of operational links required
within each trigger before the trigger initiates a failover event. For example, if the
limit is two, a failover event occurs when the number of operational links in the
trigger is two or fewer. When you set the limit to zero, the switch triggers a failover
event only when no links in the trigger are operational.
Primary
Switch
Trigger 1
Backup
Switch
Trigger 1
Server 1
NIC 1
NIC 2
Server 2
NIC 1
NIC 2
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