IBM Ethernet Switch B48Y
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The optional 4-port 10 GbE SFP+ Interface Module (81Y1455) is required to build a stack. No additional
licenses are required. Stacking can be done over one or two of the 10 Gbps ports on the switch, providing
20 Gbps of bandwidth between stack members. The remaining two or three 10 Gbps ports can be used to
carry regular data traffic. Stacking is supported in both ring and linear topologies (Figure 5).
Figure 5. IronStack technology found on the B48Y enables a logical chassis of up to 384 ports
Consider using a ring or closed-loop topology to ensure un-interrupted stack operation in the event of a
switch or link failure. Within the stack is an Active Controller, which handles stack management and
configures all system and interface-level features, and a Standby Controller, which takes over if the Active
Controller fails. Feature configuration in a stacked setup similar to a chassis whereby interfaces are
identified in a <stack unit #>/<port region>/<port number> manner.
Regular 10GBASE-SR transceivers (69Y0389) and multi-mode fiber cable can be used to connect two
stack members over distances of up to 300 meters. This enables splitting a stack across multiple rooms
or floors for flexibility. In stacks of more than two switches, the distance between the other stacked units
can be up to 100 meters, allowing for a total ringed cable loop of 1,000 meters between eight stacked
units, ideal for most stack deployments.
More common within the data center is stacking across a row of servers, which can be done using
lower-cost SFP+ TwinAx cables (Table 4) if the switches are less than 5 meters apart. To stay within the
cabling distances of these Direct Attach Cables, a cabling method such as that illustrated in Figure 6 can
be used.
Figure 6. Using IronStack to unify the network layer across a row of servers into a single logical device