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How to Configure Network Interface Cards in Unmanaged Mode

  • CTX117583
  • Created onMar 26, 2014
  • Updated onMar 28, 2014
Article Topic Networking

Objective

This article describes XenServer managed and unmanaged network interfaces and the main differences between the two.

Background

By default, XenServer recognizes and configures all available network interface cards (NICs) in managed mode used for both management and Virtual Machine (VM) traffic. Occasionally, administrators require dedicated NICs for various purposes, storage traffic being the most common.

The remaining paragraphs in this section describe the differences between the two types of XenServer interfaces:

Xen Managed

An interface is configured using the command line interface.

Advantages:
Managed interfaces are persistent across upgrades as they are part of the Xen database.

Disadvantages:
Users can see the managed interfaces in Xen Center and may accidentally use it for VM traffic which will impact the performance dedicated for storage. Moreover, someone may accidentally destroy the network or interface.

Xen Unmanaged

An interface is configured manually. Following the configuration, the interface is removed from the database and cannot be used for Xen managed networks, unless rescanned (pif-scan).

Advantages:
This approach ensures that the NIC in question remains invisible to Xen management tools (CLI and GUI) and can be fully dedicated to its sole purpose – no other traffic can go through this link.

Disadvantages:
Configuration and maintenance in case of XenServer upgrade is more challenging. Upgrading your XenServer host will most likely erase the established configuration which will have to be manually reinstated.

Instructions

To configure a NIC in unmanaged mode, perform the following steps:

  1. Run the xe pif-list command and determine the Universal Unique Identifier (UUID) of the NIC to be placed in unmanaged mode. Note that in a server pool with more than one server (one server is a standalone pool), this procedure must be done on each pool member. Use xe host-list to determine UUID on each pool member for use with the xe pif-list commands. 

    Note: The management PIF cannot be set to unmanaged mode.
    # xe pif-list host-uuid=e616e28e-1dd9-4e2a-b426-0c134b18da6f

    uuid ( RO)                  : 97afe085-c679-3aa0-d09b-3c530ee3ac60
                    device ( RO): eth2
        currently-attached ( RO): true
                      VLAN ( RO): -1
              network-uuid ( RO): 2e726039-479e-10a4-2fd5-e638b3243ca8
    uuid ( RO)                  : 602eee87-2618-22ce-3ab1-f7af9dfddb90
                    device ( RO): eth1
        currently-attached ( RO): true
                      VLAN ( RO): -1
              network-uuid ( RO): 65c43f27-3c42-326d-8e6d-7a5757611683
    uuid ( RO)                  : 08146461-afa0-dfed-ca91-061b7d42a972
                    device ( RO): eth0
        currently-attached ( RO): true
                      VLAN ( RO): -1
              network-uuid ( RO): 2795e245-a591-5041-d38b-f3444e3c219c

    If you have missing NICs in the above output, the NIC may already be unmanaged or not recognized by XenServer. To ensure all NICs are rescanned and placed into managed mode, run xe pif-scan (see the following Warning).

    WARNING! Running xe pif-scan on a XenServer host that already has unmanaged NICs may lead to unwanted effects because it will re-discover and re-introduce NICs back into managed mode.
  1. Run the xe pif-forget uuid=PIF-UUID command to remove the interface from XenServer database.

    Example with interface eth2 in unmanaged mode.
    # xe pif-forget uuid=97afe085-c679-3aa0-d09b-3c530ee3ac60

    Then list all PIFs to ensure the unmanaged one is no longer in the list:
    # xe pif-list host-uuid=e616e28e-1dd9-4e2a-b426-0c134b18da6f

    uuid ( RO)                  : 602eee87-2618-22ce-3ab1-f7af9dfddb90
                    device ( RO): eth1
        currently-attached ( RO): true
                      VLAN ( RO): -1
              network-uuid ( RO): 65c43f27-3c42-326d-8e6d-7a5757611683
    uuid ( RO)                  : 08146461-afa0-dfed-ca91-061b7d42a972
                    device ( RO): eth0
        currently-attached ( RO): true
                      VLAN ( RO): -1
              network-uuid ( RO): 2795e245-a591-5041-d38b-f3444e3c219c
  2. Configure the NIC according to your needs. Create and edit the /etc/sysconfig/network-scripts/ifcfg-eth2 file with the following example:
    DEVICE=eth2
    ONBOOT=yes
    TYPE=Ethernet
    HWADDR=XX:XX:XX:XX:XX:XX
    IPADDR=XXX.XXX.XXX.XXX
    NETMASK=XXX.XXX.XXX.XXX
    GATEWAY=XXX.XXX.XXX.XXX
    BOOTPROTO=none
    USERCTL=no

  3. In many cases, when the interface is managed and after it is made unmanaged, the network configuration files still remain on the backend.
    For example, XenServer does not remove its configuration from disk. It is recommended to replace the contents of the file with the preceding configuration, in order to avoid improper functioning and confusion. In this case, eth2 is being unmanaged, therefore you should replace the contents of the /etc/sysconfig/network-scripts/ifcfg-eth2 file with the example contents shown in the example.

  4. Save the file and activate the interface:
    # ifup eth2

Additional Resources

To configure Ethernet interfaces in CentOS, refer http://www.centos.org/docs/5/html/5.1/Deployment_Guide/s2-networkscripts-interfaces-eth0.html or /usr/share/doc/initscripts-8.45.17.EL/sysconfig.txt on your Xenserver.

Dell customers - refer http://supportapj.dell.com/support/edocs/software/Citrix/EN/Solutions%20Guide/HTML/body.htm.

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