If you are running UCS hardware with ESXi then you should be using custom ENIC/FNIC drivers as specified on the Hardware and Software Interoperability Matrix. If you are running ESXi 5.x and leveraging the FNIC driver than I would highly suggest you look at which version of UCS you are running and what version of the FNIC driver you are running.
Before I get into the issue let me start by briefing discussing the UCS drivers. The ENIC, or Ethernet NIC, driver is used by the the hypervisor to communicate with the physical NIC in the server. The FNIC, or Fiber Channel (FC) NIC, is used by the hypervisor to communicate with the physical HBA in the server. All servers should have NICs, but whether or not they contain HBAs depends on the type of storage you are leveraging. If you are connecting to FC or hardware iSCSI datastores than this article is relevant to you.
The particular issue I am bringing up has to do with FNIC driver 126.96.36.199. Whether or not you should be running FNIC driver 188.8.131.52 depends on a variety of factors including:
- UCS version
- Type of HBA
- Version of ESXi
The specific bug I am referring to is: CSCue21073. Per the link you will notice that the bug states this impacts C-series servers. With a quick search of the Interoperability Matrix I turned up the following matches:
- C-series running 1.4(7) or 1.4(8) on vSphere 5.0
- C-series running 1.4(6) on vSphere 5.0 of 5.0U1
- C-series running 1.4(5) on vSphere 5.0
One thing the bug does not mention is that this issue also impacts B-series systems as well. Specifically:
I am mentioning this particular bug as I have personally experienced this issue on several systems. The good news is that the issue is hard to reproduce, but it is something to be aware of. A reboot of the host addressed the issue in the environment I was working in. Per the bug this issue has been fixed and will be part of a future release. What is not clear is whether a FNIC driver update will be required and/or whether you will need to upgrade UCS. In either case, you can expect a reboot will be needed somewhere. If running a service vulnerable to this issue I would personally recommend upgrading to a newer version of UCS that has an upgraded FNIC driver to ensure this issue does not impact you.
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