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Alteon OS Application Guide
218
Chapter 13: High Availability 42C4911, January 2007
Layer 2 Failover
The primary application for Layer 2 Failover is to support Network Adapter Teaming.
With Network Adapter Teaming, the NICs on each server all 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 NetXen 10 Gb Ethernet Adapter documentation.
NOTE – Only two links per server blade 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 GbE Switch Module, including
LACP trunks. Trunks can be added to failover trigger groups such that if some (or all) of the
links fail in a trigger, the switch disables all internal ports in the switch (unless VLAN Monitor
is turned on). When the internal ports are disabled, it causes the NIC team on the affected
server blades to failover from the primary to the backup NIC. This process is called a failover
event.
When the appropriate number of links in a trigger group return to service, the switch enables
the internal ports. This causes the NIC team on the affected server blades to fail back to the pri-
mary switch (unless Auto-Fallback is disabled on the NIC team). The backup switch processes
traffic until the primary switch’s internal links come up, which takes up to five seconds.
VLAN Monitor
The VLAN Monitor allows L2 Failover to discern different VLANs. With VLAN Monitor
turned on:
If enough links in a trigger go down (see “Setting the Failover Limit” on page 219), the
switch disables all internal ports that reside in the same VLAN membership as the trunk(s)
in the trigger.
When enough links in the trigger return to service, the switch enables the internal ports
that reside in the same VLAN membership as the trunk(s) in the trigger.
If you turn off the VLAN Monitor (/cfg/failovr/vlan/off), only one failover trigger
is allowed. When a link failure occurs on the trigger, the switch disables all internal server-
blade ports.