are the IP address normal after installation of virtualization

very new to linux, not sure if this should be post in the virtualiztion section, please move if it should belong to there.
I installed OpenSUSE13.2 64bit on my HP server (the HP server is in a windows domain LAN with), everything works fine afterwards, the server has two Ethernet port, therefor has two IP.
then I’d like to test out the Virtualization on my HP server, so I installed KVM Server, KVM tools and libvirt LXC daemon via Yast, during the installation, it asks me to use bridge so i followed on screen wizard and the installation went smoothly and complete successfully.
here I have a beginner question. I typed ifconfig via the konsole both before the KVM installation and after the installation in order to compare the IP addresses, here is the result of before and after, is this normal for two network port configuration? anything wrong? (the IP address was set static before the KVM installation)
I assume this should be the way for the network to function, however, when I create the first vm, using the CD media, it booted fine, but not able to install linux as the installation freeze there and I had to cancel it. not sure if that is caused by the network config? is this has to do with firewall? if so, how? some hints?
any comments would be appreciated, many thanks.

by the way, here is the settings for the first vm when i try to create it, and after, it booted fine from the CD and i remember it even passed the time zone selection step, but freeze afterwards during the installation. anything wrong with the settings for this vm or it related to the firewall?

Here are some basics on computers and networking in general…

When you have multiple ethernet ports (NICs), they are intended to be connected to different unconnected physical networks, like one facing the Internet and the other facing your LAN (thus performing as a router).

In general, you never attach both NICs to the same physical network, except in rare situations (like bonding the two NICs). When you do this, your physical machine is advertising to all others in the same network (broadcasts, paticularly ARP in IPv4, multi-casts in IPv6) separately that each NIC is to be associated with your machine. But, because your machine is one and the same for both NICs, this means that in a TCP/IP session a packet might leave one NIC and then a returning packet sent to your other NIC which would disgard the packet (because the 2nd NIC didn’t know about the original packet that left the 1st NIC). If this happened, then by chance numerous packets could be dropped and needed to be resent.

Also, since there can only be one packet traveling on a physical ethernet segment at a time, ordinarily there is no speed benefit.

So, just choose one of your NICs to be active and configured on your network and you’ll be fine.
Leave the other unattached unless you have reason to connect to something.

As for the scenario running virtual networking on this machine, I’ve described virtual networking in several posts in the Virtualization forum. There is an architecture of connecting Guests to Linux Bridge Devices (often called network bridges by openSUSE documentation) which are then bound eventually to a physical NIC in this way, the Host and any number of Guests share the use of the same NIC. Especially for the newbie, this can be set up for you automatically no matter what virtualization technology you choossearch for posts about your specific choice to know exactly where and how to do a recommended install).


You’ll notice on your machine that two Linux Bridge Devices have been created on your machine (br0, br1).

To see display the general properties of the bridge devices including what physical NICs they are connected to

brctl show

You can also find the above information in YAST > Network Devices

But, to actually setup and use these bridge devices as virtual networks, you likely need to do this in the recommended virtualization manager (unless you were expert, then you can also setup from command line).


thanks tsu2 for your help !