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Cisco Bug: CSCuq74763 - Unable to initiate TCP traffic from Windows 2012 hypervisors

Last Modified

Feb 11, 2016

Products (1)

  • Cisco Unified Computing System

Known Affected Releases

2.2(3a)A

Description (partial)

On Windows 2012 hypervisors, when NVGRE  NIC task offloads are enabled, NVGRE Traffic could not be sent from the VMNICs configured on NVGRE virtual networks. This issue is specific to Windows 2012 hypervisors, where the hypervisor inserts the checksums, eventhough the NIC hardware offloading is enabled for generating the checksums.

This issue is not applicable to hypervisors running Windows 2012 R2.

Symptom:
On Windows 2012 hypervisors, the VMNICs configured with NVGRE Network Virtualization could not initiate the network traffic, when NVGRE NIC task offloads are enabled. The ping operation would work fine when patch KB2779768  is installed. But the TCP/UDP traffic would not work even with this patch. The server receiving the NVGRE packets from Windows 2012  would drop the packets because the IP-checksum of the inner header would be zero.

Conditions:
This is applicable only for Windows 2012 hypervisors
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