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XenServer and Multicast with IGMP support

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.

  1. 1. Install the XenServer tools on the virtual server;
  2. 2. Execute the ifconfig command, like shown below, to enable multicast on the virtual interface;

# 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.

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René Jorissen

Co-owner and Solution Specialist at 4IP Solutions
René Jorissen works as Solution Specialist for 4IP in the Netherlands. Network Infrastructures are the primary focus. René works with equipment of multiple vendors, like Cisco, Aruba Networks, FortiNet, HP Networking, Juniper Networks, RSA SecurID, AeroHive, Microsoft and many more. René is Aruba Mobility First Expert (AMFX #26), Aruba Certified Mobility Expert (ACMX #438), Aruba Certified ClearPass Expert (ACCX #725), Aruba Certified Design Expert (ACDX #760), CCNP R&S, FCNSP and Certified Ethical Hacker (CEF) certified. You can follow René on Twitter and LinkedIn.

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3 Responses to XenServer and Multicast with IGMP support

  • Hi There, Did you ever do further testing? It concerns me that we are making a change to the VIF when it changes with the DOMID on reboot. Also, were you using openvswitch or linux bridge? We are about to test NLB on XenServer 6.0.2 so this is critical to the solution.

    Thanks in advance

  • I didn’t do further testing on this subject. So I am not sure about the outcome of the VIF change.

  • Hi Rene,

    we are also running an NLB with physical + XenServer virtual nodes. Our problem is that we will periodically (small percentage of requests) have long delays communicating with some clients.
    Do you know if the NLB with physical + XenServer virtual nodes was successful?

    Thanks.

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