The Cisco Nexus 1000V distributed virtual switch for VMware vSphere infrastructure brings quite a significant advantage to the networking implementation of the virtual environments. Comparing to the standard VMware vSwitch and DVS virtual switches, the Nexus family virtual switch adds most of the functionalities in the virtual environment that are found in today’s physical switch products. This fills up the gap between the physical network infrastructure and the virtual machine, allowing the network engineers to have more control on the virtual environments.
Despite that VMware and Cisco co-developed this solution for years, I would say that it is still in early stage and has some bugs out there. Those, of course, are rapidly being fixed by Cisco and new releases are coming one after another. Although, that is not an excuse and neither helps, when you face strange and hardly digestible issues happening in the production…
One of the issues that I had to know was that packets from or / and to virtual machines were lost randomly. We were running Nexus 1000V version 4.0(4)SV1(2). At that time there was a new update out – version 4.0(4)SV1(3). So, naturally the idea was to upgrade to the latest version hoping that the issues will vanish. However, before this to be done I have stumbled upon a Cisco bug entry with the ID CSCte44240, which states this:
Unicast or multicast packet drops might seen if IGMP is enabled on setup with vPC-HM ports.
This was probably the case with our setup, because disabling IGMP snooping helped and packet loss seems to be gone (for now). It is possible to disable the IGMP snooping either globally or for a specific VLAN.
Open and resolved ceveats for version 4.0(4)SV1(3) can be found here: http://www.cisco.com/en/US/docs/switches/datacenter/nexus1000/sw/4_0_4_s_v_1_3/release/notes/n1000v_rn.html#wp42881.
