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Cisco Bug: CSCuo72256 - Windows VM reboot on N1k loses statically configured IP address

Last Modified

Feb 11, 2018

Products (2)

  • Cisco Nexus 1000V Switch for VMware vSphere
  • Cisco Nexus 1000V Switch

Known Affected Releases

4.2(1) 4.2(1)SV2(2.0.254) 4.2(1)SV2(2.2)

Description (partial)

Symptom:
We have observed a number of Windows VMs in our environment that lose network connectivity after a reboot.
This appears to be caused by Duplicate Address Detection during bootup. Windows is sending ARP requests for its own address to ensure there is no conflict on the local vlan.
If ARP replies are (not) received, bootup continues as normal. However if an ARP reply is seen, Windows assumes there is a conflict and disables the IP address on that particular network interface.

Conditions:
We have observed that the Nexus 1k VSM sends an ARP request for the VM's IP address on link-up (even though the CTS device tracking and DHCP snooping is disabled on N1k).
Normally this occurs a few seconds prior to Windows duplicate address detection but on occasion the N1k ARP request is sent after the first ARP request from the Windows VM which causes Duplicate Address Detection to fail.
Windows boots up with a 169.254.x.x address and network connectivity is lost. Rebooting the VM often fixes the problem.
00:02:3d:90:00:02 is the N1k Internal Port MAC
00:50:56:ad:32:5e is the VM MAC
Normal bootup sequence:
16:49:56.633033 00:02:3d:90:00:02 > 00:50:56:ad:32:5e, ethertype ARP (0x0806), length 64: Ethernet (len 6), IPv4 (len 4), Request who-has 10.37.4.189 tell 0.0.0.0, length 50

VSM and VEM versions: 
version 4.2(1)SV2(2.2)
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