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Figure 1:
Cisco Nexus Virtual Chassis Topology
The Cisco Nexus switches, along with the Cisco Nexus 2000 Series and B22 for IBM, create a distributed
modular system that unifies the data center architecture. Within this distributed modular system, both IBM Flex
System
®
computing nodes and rack servers are managed identically. This approach allows the use of the same
business and technical processes and procedures.
The left-most blade chassis in Figure 1 contains dual Cisco Nexus B22 for IBM fabric extenders. Each Cisco
Nexus B22 for IBM is singlely attached to a parent Cisco Nexus 5500 platform switch, a connection mode referred
to as straight-through mode. The fabric links can be either statically pinned or put into a Port Channel. This
connection mode helps ensure that all data packets from a particular Cisco Nexus B22 for IBM enter the same
parent Cisco Nexus switch. This approach may be necessary when certain types of traffic must be restricted to
either the left or right Cisco Nexus 5500 platform switch: for instance, to maintain SAN A and SAN B separation.
Also, in this example the connections to individual computing nodes are in active-standby mode, which helps
ensure traffic flow consistency but does not make full use of the server network interface card (NIC) bandwidth.
The second IBM Flex System chassis from the left in Figure 1 improves on the first with the creation of an
Ethernet virtual Port Channel (vPC) from the computing node to the Cisco Nexus parent switch. This vPC places
the Ethernet portion of the NICs in an active-active configuration, giving increased bandwidth to each host. The
FCoE portion of the CNA is also configured as active-active but maintains SAN A and SAN B separation because
each virtual Fibre Channel (vFC) interface is bound to a particular link at the server. This configuration also
achieves high availability through redundancy, and it can withstand a failure of a Cisco Nexus 5500 platform
switch, a Cisco Nexus B22 for IBM, or any connecting cable. This topology is widely used in FCoE deployments.
The third blade chassis from the left in Figure 1 contains Cisco Nexus B22 for IBM fabric extenders that connect
to both Cisco Nexus 5500 platform switches through vPC for redundancy. In this configuration, active-active load
balancing using vPC from the blade server to the Cisco Nexus 5500 platform switch cannot be enabled. However,
the servers can still be dual-homed with active-standby or active-active transmit-load-balancing (TLB) teaming.
This topology is only for Ethernet traffic because SAN A and SAN B separation between the fabric extender and
the parent switch is necessary.
