Linux bonding, vlans, bridges & KVM
In this blog post I’ll share with you how to setup the networking part of your virtualization solution using KVM.
We will talk about bonding, vlans and bridges.
Setting up a KVM host is an easy one. What people often forget to think about is the networking part of it. I’m not going to explain what bonds, vlans and bridges are here - there’s plenty of good documentation out there which explains it better.
So if you are new to bonds, vlans and bridges I’d suggest you spend some time checking the links below:
The target system I’m using as a KVM hypervisor is Debian Wheezy, which is already configured for hosting KVM guest domains. The last thing that remains is to configure the networks for the KVM guests.
The networking setup of the KVM hypervisors we have is more-or-less described like this. First we configure bonding on the interfaces for link aggregation and failover, then we create VLANs of the bond for splitting the network into logical segments for our VMs, and lastly we configure bridges of the VLANs, which will be attached to the running KVM guest domains.
So, lets start, shall we? Install First, lets install some packages:
$ sudo apt-get install ifenslave-2.6 vlan bridge-utils
Then we create two bonding interfaces - bond0 and bond1 and put our networking configuration in /etc/network/interfaces, which looks like this:
auto lo iface lo inet loopback auto eth0 iface eth0 inet manual bond-master bond0 auto eth1 iface eth1 inet manual bond-master bond1 auto eth2 iface eth2 inet manual bond-master bond0 auto eth3 iface eth3 inet manual bond-master bond1 auto bond0 iface bond0 inet static address 10.10.100.100 netmask 255.255.255.0 gateway 10.10.100.1 slaves none bond-mode active-backup bond-miimon 100 bond-downdelay 200 bond-updelay 200 auto bond1 iface bond1 inet manual slaves none bond-mode active-backup bond-miimon 100 bond-downdelay 200 bond-updelay 200
Now we have two bonds, so lets create the VLANs and bridges for our KVM guest domains. Append the following lines to /etc/network/interfaces file for setting up the VLANs and KVM bridges.
# vlan50 - management network auto vlan50 iface vlan50 inet manual vlan_raw_device bond1 # br50 - management network auto br50 iface br50 inet static address 192.168.100.1 netmask 255.255.255.0 network 192.168.100.0 bridge_ports vlan50 bridge_maxwait 5 bridge_stp off bridge_fd 0 # vlan100 - Test network auto vlan100 iface vlan100 inet manual vlan_raw_device bond1 # br100 - Test network auto br100 iface br100 inet static address 192.168.200.1 netmask 255.255.255.0 network 192.168.200.1 bridge_ports vlan100 bridge_maxwait 5 bridge_stp off bridge_fd 0
The reason we create VLANs is because we want to have different networks for our VM machines - test network, engineering, production, etc. Out of the VLANs we create bridges as well, so that we can attach our KVM VMs to them.
Once you are ready you can restart the network or reboot your machine
in order to apply the changes. Once the changes are in place you can
check the status of your bonds in
# cat /proc/net/bonding/bond0 Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011) Bonding Mode: fault-tolerance (active-backup) Primary Slave: None Currently Active Slave: eth0 MII Status: up MII Polling Interval (ms): 100 Up Delay (ms): 200 Down Delay (ms): 200 Slave Interface: eth0 MII Status: up Speed: 100 Mbps Duplex: full Link Failure Count: 0 Permanent HW addr: 00:25:90:95:7f:70 Slave queue ID: 0 Slave Interface: eth2 MII Status: up Speed: 100 Mbps Duplex: full Link Failure Count: 0 Permanent HW addr: 00:25:90:93:6e:04 Slave queue ID: 0
And for the VLANs:
$ sudo cat /proc/net/vlan/vlan50 vlan50 VID: 50 REORDER_HDR: 1 dev->priv_flags: 4001 total frames received 275 total bytes received 25471 Broadcast/Multicast Rcvd 76 total frames transmitted 266 total bytes transmitted 34553 Device: bond1 INGRESS priority mappings: 0:0 1:0 2:0 3:0 4:0 5:0 6:0 7:0 EGRESS priority mappings:
Finally lets check our bridge:
# brctl show br50 bridge name bridge id STP enabled interfaces br50 8000.002590957f71 no vlan50