Hello,

Exchange CAS array (NBL) has been already configured with node CAS node. When i was trying to add third node, in NLB console showing Misconfiguration. Then i delete 2nd node which was working well then i was trying to add third node but same issue and when it showing misconfiguration then the NLB NIC got Ping loss. NLB was configured in unicast mode.

All the server is in physical environment

The error below:

Hello

tip:check network card driver v

Hi,

Can you ping all the NLB server on the NLB NIC , I assume it is a dedicated nic for NLB and one NIC for LAN?

It has something to do with mac spoofing so I suggest check the Nic Settings and check the MAC tables.

Hello,

I have check and also change the NIC Card. and you know, the environment is Physical. So, Please suggest.

NLB configured in unicast mode.

Please suggest

Hello All,

Can anyone give suggestion

Parvez,

NLB can be somewhat tricky to configure. For certain, the best method would be using NLB in IGMP Multicast mode. But "IGMP Multicast" is a switch-assisted method, which would require you to configure the switch. And that is total different story. You are currently using NLB in Unicast mode, which is a non-switch-assisted method, which requires no configuration on a switch. Sounds easy. But there are a few problems with it, like these:

• NLB in Unicast mode causes a well know issue called 'switch-flooding'.
• Some low-budget L3 switches do not support NLB in unicast mode.
• NLB in unicast mode is not supported on VMware. Multicast is required, unless you configure a work-around.
• Because the NLB nodes use the same unicast MAC Address (which causes switch-flooding); in some situation NLB members 'cannot' communicate. This is why a second NIC is required for communication. This is why you get a warning when you open NLB manager.

Anyway. I don't know you scenario, but allow me to ask a few questions:

• You added this to the High Availability (Cluster) forum. Are you using NLB on top of Failover Cluster Manager? You don't, right?
• Are you running the NLB members as a Virtual Machine? If so, make sure the vNIC is allowed to spoof its MAC Address.
• If you are using VMs; On which Hypervisor are you hosting them? Before you configure, please move the VMs to the same host before you configure it, so they are connected to the same vSwitch.

Sometimes if NLB in Unicast doesn't work well. Try to add the NLB member from the other side as well. Of course it ain't nice, but it can work.

Hello Boudewijn Plomp,

Thanks for your reply. the NLB environment is Physical. there is no virtual environment.

Please suggest what I will suppose to do. You know in those server Exchange server 2010 has been installed.

HI,

Are you running the NLB on two nic's one for NLB and one for Lan traffic ?

and did you check the MAC on the nic adapters just to make sure the don't have the same mac ? just like the NLB creation.  The problem you have is based on some misconfiguration.

As I ask before "Can you ping all the NLB server on the NLB NIC , I assume it is a dedicated nic for NLB and one NIC for LAN? "

and are you using an arp table on the Switches ?

Hello i have used dedicated LAN for NLB. I have ping all the NLB server. when the third node add, which is always showing misconfiguration then ping lost of third NLB NIC.

All the server are physical environment. please suggest