Today I tried to add a virtual Terminal Server within a XenServer to a NLB cluster. The current NLB cluster contained only physical servers. When adding the virtual server to the NLB cluster with the NLB manager, the server lost all IP communication. It isn’t possible to connect to or from the server. Together with the system administrator, we searched multiple forums and we found the solution to the problem.
It looks like XenServer doesn’t support multicast by default, because of the bridge design of the network interfaces. We found an interesting article on the internet to enable multicast on the virtual interface.
In the end we took the following steps to enable multicast support on the virtual interface of the XenServer.
# Retrieve the DOMID of the virtual server
xe vm-list name-label=<VMNAME> params=dom-id
# Enable multicast on the virtual interface of the virtual server
ifconfig vif<DOMID>.0 multicast
We restarted the virtual server and the DOMID changed, but multicast with IGMP support was still working and the server was still part of the NLB cluster. The system administrator will do some more testing and he will try to add another virtual server to the NLB cluster.
Today I have been troubleshooting problems with a Microsoft ISA array. The array didn’t function anymore after moving the Configuration Storage Server and one array member from a VMware 3.5 environment to a VMware 4.0 environment. After moving the array member the VMware Tools were upgraded and also the Virtual Hardware was upgraded. After rebooting the moved array member the customer received multiple error messages, like duplicate IP addresses and users not able to access resource through the reverse proxy.
A Microsoft ISA array uses Network Load-Balancing and NLB was the cause of all problems. After upgrading the VMware Tools and the Virtual Hardware, NLB needs to be reconfigured. The complete configuration of NLB was lost. I reconfigured NLB (multicast with IGMP support) and the problem was resolved. The array members were functioning properly again.
Moving and upgrading the second array member resulted in the same problems with the same cause. Reconfiguring NLB on the second array member did the trick. So be careful when moving ISA array members with NLB configured from a VMware 3.5 to a VMware 4.0 environment, especially when upgrading VMware Tools and the Virtual Hardware.