17–QLogic Teaming Services
General Network Considerations
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Teaming Across Switches
SLB teaming can be configured across switches. The switches, however, must be
connected together. Generic Trunking and Link Aggregation do not work across
switches because each of these implementations requires that all physical
adapters in a team share the same Ethernet MAC address. It is important to note
that SLB can only detect the loss of link between the ports in the team and their
immediate link partner. SLB has no way of reacting to other hardware failures in
the switches and cannot detect loss of link on other ports.
Switch-Link Fault Tolerance
The diagrams below describe the operation of an SLB team in a switch fault
tolerant configuration. We show the mapping of the ping request and ping replies
in an SLB team with two active members. All servers (Blue, Gray and Red) have a
continuous ping to each other.
is a setup without the interconnect
cable in place between the two switches.
has the interconnect cable
in place, and
is an example of a failover event with the Interconnect
cable in place. These scenarios describe the behavior of teaming across the two
switches and the importance of the interconnect link.
The diagrams show the secondary team member sending the ICMP echo
requests (yellow arrows) while the primary team member receives the respective
ICMP echo replies (blue arrows). This illustrates a key characteristic of the
teaming software. The load balancing algorithms do not synchronize how frames
are load balanced when sent or received. In other words, frames for a given
conversation can go out and be received on different interfaces in the team. This
is true for all types of teaming supported by QLogic. Therefore, an interconnect
link must be provided between the switches that connect to ports in the same
team.
In the configuration without the interconnect, an ICMP Request from Blue to Gray
goes out port 82:83 destined for Gray port 5E:CA, but the Top Switch has no way
to send it there because it cannot go along the 5E:C9 port on Gray. A similar
scenario occurs when Gray attempts to ping Blue. An ICMP Request goes out on
5E:C9 destined for Blue 82:82, but cannot get there. Top Switch does not have an
entry for 82:82 in its CAM table because there is no interconnect between the two
switches. Pings, however, flow between Red and Blue and between Red and
Gray.
Summary of Contents for 8400 Series
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