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IPV6 Neighbor Discovery packets or Multicast Packets with destination MAC as multicast MAC is dropped at the receiver VNIC. Using the drop filter, check if the packet is dropped on the switch port corresponding to the destination VM. pktcap-uw --switchport <switchport> --capture DROP Run the below command on the ESX host where the problem VM is located. Non-Working VM: net-stats -lFrom the output of above command, get the portNum and switchName values that correlate with your VM, and substitute their values in the below command vsish cat /net/portsets/<switchName>/ports/<portNum>/status Example: cat /net/portsets/DvsPortset-1/ports/100663504/status port { port index:208 vnic index:0x00000001 portCfg:c468b258-2885-4bd2-a206-e93b2fa57ab5 dvPortId:b9fc34a5-404f-4aeb-8d53-45db7d975f74 clientName:pub-icdns1-south.eth1 clientType: 5 -> VMM Virtual NIC clientSubType: 9 -> Vmxnet3 Client world leader:5803472 flags: 0x40093 -> IN_USE ENABLED WORLD_ASSOC DVS_PORT CONNECTED Impl customized blocked flags:0x00000000 Passthru status: 0x8 -> DISABLED_BY_HOST fixed Hw Id:00:50:56:b7:3e:45 ethFRP:frame routing { requested:filter { flags:0x0000000b -----------------> The "0x0000000b" doesn't have VMK_ETH_FILTER_ALLMULTI flag. unicastAddr:00:50:56:b7:3e:45: numMulticastAddresses:4 multicastAddresses:01:00:5e:00:00:01,33:33:00:00:00:01,33:33:ff:35:02:12,33:33:ff:b7:3e:45, LADRF:[0]: 0x0 [1]: 0x0 } accepted:filter flags:0x0000000b unicastAddr:00:50:56:b7:3e:45: numMulticastAddresses:4 multicastAddresses:01:00:5e:00:00:01,33:33:00:00:00:01,33:33:ff:35:02:12,33:33:ff:b7:3e:45, LADRF:[0]: 0x0 [1]: 0x0 } } For working VM: ethFRP:frame routing { requested:filter { flags:0x0000000d -----------------------> The "0x0000000d" has VMK_ETH_FILTER_ALLMULTI flag. unicastAddr:00:50:56:97:c8:c4: numMulticastAddresses:0
It depends on the number of multicast addresses enabled. If the total is less than 32, we will do perfect filtering based on exact multicast address. Otherwise we will enable the allmulti flag so that all multicast address will be received. There are two main ways in which this ALLMULTI flag can be set. (3.1) When multicast snooping is enabled, and the number of multicast addresses on a port > 512, ALLMULTI is set. (3.2) ALLMULTI is set from the VM by vmxnet3 Linux driver. Looking at vmxnet3 Linux driver code, this happens in two cases: (3.2.1) Explicit request to vmxnet3 driver to set ALLMULTI. (3.2.2) If somehow the driver's attempt to pass an exact list of multicast addresses to the vmxnet3 device fails, ALLMULTI is set instead. When this happens, the following log entry should be found in dmesg when this happens: "failed to copy mcast list, setting ALL_MULTI"
Workaround: Add Static IPV6 ND entries, but it has to be done for every device that needs to reach the VM (OR) For workaround, enable all multi on the problem Vm using the below command "ifconfig eth1 allmulti" on issue vms Before setting allmulti on VM flags, it might be eth1: flags <UP,BROADCAST,RUNNING,MULTICAST> and after setting that, it might be eth1: flags <UP, BROADCAST,RUNNING,ALLMUTICAST,MULTICAST>. Then check whether the switchport status of vsish node is set as ethFRP:frame routing { requested:filter { flags:0x0000000d
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