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Network health check feature limitations in vSphere 5.1 and 5.5 (2034795)

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Details

Limitations with network health check feature exist in vSphere 5.1 and 5.5. The limitations are:
  • The distributed switch network health check for vSphere 5.1 and 5.5 does not diagnose the end-to-end full path problem. Using the echo type L2 protocol, the health check only checks the health status of ports to which the distributed switch connects. So, the check reports good health status only if two or more good setting peers (uplinks) appear in the same L2 networking.
  • The physical switch VLAN does not recognize the virtual networking in ESXi. If the physical switch is misconfigured, ESXi does not report warnings, resulting in networking failures until you enable the health check feature and the new round check completes.
  • The distributed switch network MTU health check is designed to probe the runtime true Jumbo Frame capability of ports to which the distributed switch connects. However, the maximum VLAN MTU size determines the physical switch trunk port MTU size setting in all trunk VLANs for the port. The MTU health check feature "Supported/Not supported" result displays whether or not the access port supports the distributed switch MTU setting. The "VLAN Trunk" result field displays all the distributed port groups VLAN setting range in that physical switch trunk port.
  • The distributed switch network health check, including the VLAN, MTU, and teaming policy check can not function properly when there are hardware virtual NICs on the server platform. Examples of this include but are not limited to Broadcom Flex10 systems and Cisco UCS systems.
  • In vSphere 5.5, the teaming health check does not work for LAG ports as the LACP protocol itself is capable of ensuring the health of the individual LAG ports. However, VLAN and MTU health check can still check LAG ports.
  • There is some scaling limitation to the network health check. The distributed switch network health check generates one MAC address for each uplink on a distributed switch for each VLAN multiplied by the number of hosts in the distributed switch to be added to the upstream physical switch MAC table. For example, for a DVS having 2 uplinks, with 35 VLANs across 60 hosts, the calculation is 2 * 35 * 60 = 4200 MAC table entries on the upstream physical switch.

Solution

There is no workaround available.

Ensure that all portgroups in the virtual distributed switch with different VLANs have the same MTU in the physical switch because ESXi will not detect the MTU mismatch of full paths and Jumbo Frame packets might forwarded to other physical switch ports which are out of the virtual distributed switch. At those ports, there is a risk that the Jumbo Frame packets might be dropped if that port and VLAN do not enable Jumbo Frames.

Additionally, ensure the number of MAC addresses to be generated by the health check will be less than the size of the physical switch(es) MAC table. Otherwise there is a risk that the switches will run out of memory, with subsequent network connectivity failures.

Note: Depending on the options that you select, vSphere Distributed Switch Health Check can generate a significant number of MAC addresses for testing teaming policy, MTU size, VLAN configuration, resulting in extra network traffic.

After you disable vSphere Distributed Switch Health Check, the generated MAC addresses age out of your physical network environment according to your network policy.

Update History

02/24/2014 - Added additional information at the end of Details and Solution sections.

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