Jul
02
2015
1

UPDATE – Managing Multiple Interfaces with Fedora 21, libvirt, Qemu, NetworkManager

This post is an update to a previous post on using multiple interfaces(Ethernet cards) on the LAN, – utilizing RedHat’s popular virtualization tools – QEMU, KVM, libvirt, and virt-manager.  In this article I will demonstrate with Fedora 21, but this roughly applies to CentOS 7 as well.

I’ve resisted upgrading to recent versions of Fedora/CentOS for a long time.  The main reason is that I hate NetworkManager.  It does to much automatically; I much preferred the old ‘network’ daemon that could easily be manually set.  For instance if I create a Bridge(call it bridge1) interface assigned to my second Ethernet card(eth1) NetworkManager will automatically create a profile for each with automatic startup and DHCP enabled!  I don’t need or want a DHCP lease on either side of a bridged interface!  Among other issues are the creation of duplicate profiles when libvirt restarts.  So NetworkManger reports ‘bridge1’ & ‘bridge1’ in the NM start menu applet.

Ideally libvirt and NetworkManager would work hand in hand because Redhat sponsors both projects…

In this article we will describe the steps to allow you to connect two seperate NIC’s to a switch; assigning one of the NIC’s specifically to guest VM’s.

Goals of this post:

  • Set NetworkManager to ignore bridge and Ethernet device
  • enable systemd version of rc.local boot script to create bridge at boot
  • assign host to specific bridged Ethernet device

(more…)

Feb
26
2009
20

Using Multiple interfaces with KVM and Xen

I’ve been meaning to write a post on ethernet bridges and how they can easily be used to accommodate virtual machines with their “own” physical NIC(Network Interface Card).  I see a ton of post online about people struggling to get multiple ethernet cards to work in Xen and other hypervisors like KVM.  A common complaint is that when both NIC cards are plugged into the LAN they lose connectivity from all machines including the host.

Many sites make an attempt to explain the problem of multiple interfaces on the same network by walking you through a Xen custom configuration.  However they fail to identify the concept of bridges, layer 2 loops and why Spanning Tree Protocol is your friend!  So many virtualization nuts(like myself) spend hours trying to find a problem with Xen, Vmware, KVM, whatever… when the problem may just be how the interfaces are configured.

The goals of this post:

* define ethernet bridging

* explain ethernet loops

* discuss how this relates to VM’s and the hypervisor

* LAB: set up two ethernet cards for guest VM and my Fedora 10 KVM Server

(more…)