[SOLVED] virbr0 and virbr1 won't start

lahfordie · 09-05-2016, 04:40 AM

I'm trying to set up virtual networks and VMs to practice for an RHCSA exam, and my virbr0/1 and virbr0/1-nic interfaces won't start. Previously they auto-started; now even when I try to manually start them, I get a "no suitable device found" message.
I'm using KVM for the task. As background, initially I had both of them working and linked to two separate vnets through KVM. I had tried both NAT and routed modes to get my VMs on separate vnets to ping each other, but they wouldn't communicate. I basically decided to start from scratch in KVM, trying to remake my vnets, etc.

Now, my problem is even worse. virbr0 and virbr1 exist (only when the vnets are active apparently)... but they won't start up.

Code:

3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 58:91:cf:0f:d8:cc brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.93/24 brd 192.168.1.255 scope global dynamic wlp3s0
       valid_lft 86403sec preferred_lft 86403sec
    inet6 fe80::5a91:cfff:fe0f:d8cc/64 scope link 
       valid_lft forever preferred_lft forever
23: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN qlen 1000
    link/ether 52:54:00:c4:29:24 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever
24: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr0 state DOWN qlen 1000
    link/ether 52:54:00:c4:29:24 brd ff:ff:ff:ff:ff:ff
25: virbr1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN qlen 1000
    link/ether 52:54:00:73:d6:77 brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.1/24 brd 192.168.100.255 scope global virbr1
       valid_lft forever preferred_lft forever
26: virbr1-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr1 state DOWN qlen 1000
    link/ether 52:54:00:73:d6:77 brd ff:ff:ff:ff:ff:ff

Code:

[root@localhost network-scripts]# ifup virbr0
[root@localhost network-scripts]# ifup virbr0-nic
Error: Connection activation failed: No suitable device found for this connection.

At this point I'm not sure how I got here, and I'll still need to work on the communication between VMs, after I get back to where the VMs can communicate with the host. Meh.

Code:

virbr0:
DEVICE="virbr0"
ONBOOT="yes"
TYPE="Bridge"
BOOTPROTO="dhcp"
STP="on"
DELAY="2"

virbr0-nic:
DEVICE="virbr0-nic"
ONBOOT="yes"
BRIDGE="virbr0"

One of the two KVM vnet xml files:

Code:

[root@localhost networks]# cat default.xml
<!--
WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
OVERWRITTEN AND LOST. Changes to this xml configuration should be made using:
  virsh net-edit default
or other application using the libvirt API.
-->

<network>
  <name>default</name>
  <uuid>fe0a13cc-d742-4386-89c3-2ac348336212</uuid>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:c4:29:24'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.128' end='192.168.122.254'/>
    </dhcp>
  </ip>
</network>

John VV · 09-05-2016, 11:34 AM

what dose your study material say ?
also WHAT version of RHEL is this ?
from your commands it looks to be rhel6 or 5

7 uses different commands

and did you add the bridges on the host machine ?

lahfordie · 09-05-2016, 04:48 PM

It's CentOS 7, which should be almost identical to RHEL 7.

My study material says to use KVM to set up two VMs on the default Vnet (192.168.122.1/24) and another one on an "outsider" Vnet (192.168.100.1/24) to simulate accessing services from across the Internet. That's what I initially couldn't get to communicate with one another at all. Trying to troubleshoot that got me to this point where the virbr0 and virbr1 interfaces appear in ip addr sh, but won't come up.

I'm not certain what you're asking about adding the bridges on the host machine. KVM automatically created the virbr0/1 and virbr0/1-nic interfaces.

John VV · 09-05-2016, 06:34 PM

cent /rhel7 uses systemd and NOT systemv that is in rhel5 and 6

to restart the network on 6 you can use ifup and ifdown if gnome desktop is not handling it

7 is different

Code:

su -
systemctl restart network.service

see the redhat systemd manual
https://access.redhat.com/documentat...h_systemd.html

also on the host did you make the virtual network bridge ?
if not there is nothing for the VM to use

lahfordie · 09-06-2016, 01:09 PM

I ended up deleting all information in KVM about virtual networks and deleting all virbr network-scripts files. Now I'm back to where I started. Will make a new thread.

JockVSJock · 09-06-2016, 02:49 PM

Quote:

Originally Posted by John VV

what dose your study material say ?

Sometimes the study material isn't all inclusive or step-by-step. I know first hand as I used Jang's book to study for RHCSA v6 and found myself scratching my head, how he got to point a to point b and I can't...

Remember, no one is born a Linux expert, we all have to learn one way or another.

lahfordie · 09-06-2016, 03:08 PM

Jang's v7 book is actually what I've been using -- I'm glad to hear I'm not the only one having issues with it. Most of it is great so far, just the vm setup leaves a lot to be desired.

Now my virbr's are up, my vms just won't talk to each other. Separate thread for that