Random clients unable to get an IP address when connecting to the VMC controller

MVP Expert
MVP Expert
Problem:

Random clients that are terminated on a VMC controller are unable to get an IP address from time to time.



Diagnostics:

From the DHCP debugging logs we will be able to see that the clients are being learnt from the uplink port and also on the tunnel from the AP:

 

Aug  2 08:46:07  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

Aug  2 08:46:16  dhcpdwrap[5663]: <202541> <5663> <DBUG> |dhcpdwrap| |dhcp| Received DHCP packet from Datapath, Flags 0x10c040, Opcode 0x5a, Vlan 3732, Ingress tunnel 187, Egress vlan 3732, SMAC 28:f0:76:4c:0e:dc

Aug  2 08:46:16  dhcpdwrap[5663]: <202554> <5663> <DBUG> |dhcpdwrap|  DHCP-RELAY: Object for mac addr: 28:f0:76:4c:0e:dc found in STA channel.

Aug  2 08:46:16  dhcpdwrap[5663]: <202534> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: DISCOVER 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412e Options 37:017903060f77fc5f2c2e 39:05dc 3d:0128f0764c0edc 33:0076a700 0c:415a2d3331302d3034

Aug  2 08:46:16  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

Aug  2 08:46:16  dhcpdwrap[5663]: <202541> <5663> <DBUG> |dhcpdwrap| |dhcp| Received DHCP packet from Datapath, Flags 0xc042, Opcode 0x5a, Vlan 3732, Ingress 0/0/0, Egress vlan 3732, SMAC 28:f0:76:4c:0e:dc

Aug  2 08:46:16  dhcpdwrap[5663]: <202534> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: DISCOVER 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412e Options 37:017903060f77fc5f2c2e 39:05dc 3d:0128f0764c0edc 33:0076a700 0c:415a2d3331302d3034

Aug  2 08:46:16  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

Aug  2 08:46:16  dhcpdwrap[5663]: <202541> <5663> <DBUG> |dhcpdwrap| |dhcp| Received DHCP packet from Datapath, Flags 0xc042, Opcode 0x5a, Vlan 3732, Ingress 0/0/0, Egress vlan 3732, SMAC 28:f0:76:4c:0e:dc

Aug  2 08:46:16  dhcpdwrap[5663]: <202534> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: DISCOVER 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412e Options 37:017903060f77fc5f2c2e 39:05dc 3d:0128f0764c0edc 33:0076a700 0c:415a2d3331302d3034

Aug  2 08:46:16  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

 

Hence the bridge table keeps changing with the destination of the client mac associated with the Tunnel ID of the AP and also the Uplink port.



Solution

The reason for this issue is because there is a duplication on the DHCP discover messages that are originated by the controller. To overcome this issue, we will have to follow the following process:

  1. From the Navigator window >Manage>System>Advanced settings
  2. Scroll down or use the search bar to go to the Net.ReversePathFwdCheckPromiscoption
  3. Select Net.ReversePathFwdCheckPromisc and click Edit option
  4. In the Edit option-Net.ReversePathFwdCheckPromiscwindow update the New value field to 1 and click Save

This option makes sure that there are no duplicates packets are being sent back to the Virtual Switch machine.

Once we set the value to 1. We will have to disable and enable the Promiscuous mode on the VM Switch settings to make sure that it takes effect on the VM instance.

Once we enabled it, the clients will be able to get an IP from the network:

Aug  2 08:46:16  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

Aug  2 08:47:24  dhcpdwrap[5663]: <202541> <5663> <DBUG> |dhcpdwrap| |dhcp| Received DHCP packet from Datapath, Flags 0x10c040, Opcode 0x5a, Vlan 3732, Ingress tunnel 187, Egress vlan 3732, SMAC 28:f0:76:4c:0e:dc

Aug  2 08:47:24  dhcpdwrap[5663]: <202554> <5663> <DBUG> |dhcpdwrap|  DHCP-RELAY: Object for mac addr: 28:f0:76:4c:0e:dc found in STA channel.

Aug  2 08:47:24  dhcpdwrap[5663]: <202534> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: DISCOVER 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412f Options 37:017903060f77fc5f2c2e 39:05dc 3d:0128f0764c0edc 33:0076a700 0c:415a2d3331302d3034

Aug  2 08:47:24  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

Aug  2 08:47:24  dhcpdwrap[5663]: <202546> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: OFFER 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412f clientIP=10.37.32.33

Aug  2 08:47:25  dhcpdwrap[5663]: <202541> <5663> <DBUG> |dhcpdwrap| |dhcp| Received DHCP packet from Datapath, Flags 0x10c040, Opcode 0x5a, Vlan 3732, Ingress tunnel 187, Egress vlan 3732, SMAC 28:f0:76:4c:0e:dc

Aug  2 08:47:25  dhcpdwrap[5663]: <202536> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: REQUEST 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412f reqIP=10.37.32.33 Options 37:017903060f77fc5f2c2e 39:05dc 3d:0128f0764c0edc 0c:415a2d3331302d3034

Aug  2 08:47:25  dhcpdwrap[5663]: <202523> <5663> <DBUG> |dhcpdwrap| |dhcp| dhcprelay: mac=28:f0:76:4c:0e:dc dev=eth1, length=300, from_port=68, op=1, giaddr=0.0.0.0

Aug  2 08:47:25  dhcpdwrap[5663]: <202544> <5663> <DBUG> |dhcpdwrap| |dhcp| Datapath vlan3732: ACK 28:f0:76:4c:0e:dc Transaction ID:0xdf4e412f clientIP=10.37.32.33

 

Version history
Revision #:
2 of 2
Last update:
2 weeks ago
Updated by:
 
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