300-610 · Question #235
Refer to the exhibit. A Cisco engineer is configuring an active/active design that consists of Cisco Nexus 7000 Series Switches with Fabric Extenders using a vPC. The desired outcome is to allow the c
The correct answer is C. They cannot exist on the same ASIC instance.. The most probable reason for an issue when configuring both straight-through FEX and active/active FEX with identical FEX IDs on Cisco Nexus 7000 switches is that these different FEX attachment modes cannot coexist on the same ASIC instance.
Question
Refer to the exhibit. A Cisco engineer is configuring an active/active design that consists of Cisco Nexus 7000 Series Switches with Fabric Extenders using a vPC. The desired outcome is to allow the connection of servers/storage/devices to a single FEX, and use the FEX port channels to each parent switch to provide redundancy. The engineer configures FEX and FEX ID to be identical on both sides. During initial tests, an issue occurs with the straight-through FEX and active/active FEX configuration. What is the most probable reason?
Exhibit
Options
- AThey are not enabled on vPC+ deployments.
- BFEX-AA is not a supported F-Series module.
- CThey cannot exist on the same ASIC instance.
- DFull duplex is disabled for FEX connectivity.
How the community answered
(19 responses)- A16% (3)
- B5% (1)
- C74% (14)
- D5% (1)
Why each option
The most probable reason for an issue when configuring both straight-through FEX and active/active FEX with identical FEX IDs on Cisco Nexus 7000 switches is that these different FEX attachment modes cannot coexist on the same ASIC instance.
FEX are commonly used with vPC deployments, so a general incompatibility with 'vPC+' (a term sometimes associated with ACI or Nexus 9K FEX) is not the core issue.
FEX Active/Active (FEX-AA) is a supported feature on many Nexus platforms; the problem arises from a specific configuration conflict, not a lack of general feature support.
Cisco Nexus FEX deployment guidelines state that on certain I/O modules, an ASIC instance can only host either straight-through FEX (connected to a single parent switch) or vPC FEX (active-active, dual-homed) host interfaces, but not both concurrently. Configuring both with identical FEX IDs on the same ASIC leads to a resource conflict.
Full duplex is a standard and required setting for FEX connectivity; disabling it would cause basic link functionality issues, not a conflict between FEX deployment types.
Concept tested: Cisco Nexus FEX ASIC limitations and deployment modes
Source: https://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/guide_c07-730243.html
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