How to troubleshoot kvm networking

Abiquo uses it's own way to configure the network, through abiquo-aim. Basically, when the first virtual machine is created, for a certain virtual network card, abiquo creates two configurations:

- vlan configuration: Abiquo creates the file /etc/sysconfig/network-scripts/ifcfg-abiquo_ethX.Z for the vlan Z in the device X.
- bridge: Abiquo creates the file /etc/sysconfig/network-scripts/ifcfg-abiquo_Z for a bridge that will connect devices in vlan Z.

KVM will create the virtual interface vnet, and connect it to the bridge.

We can check this configuration with the command:

[root@bc2blade3 ~]# brctl show
bridge name    bridge id        STP enabled    interfaces
abiquo_2        8000.0019b9f6956e    no        eth0.2
                            vnet0
virbr0        8000.525400fef26b    yes        virbr0-nic

In that case, we can see that we have one virtualmachine with one vnet on vlan 2, connected with interface eth0.2

Abiquo will create those configuration when deploying the first virtualmachine to use a certain vlan, and it will delete them when the last virtualmachine to use a certain vlan is undeployed.

Abiquo should handle those configurations without problems, but in case we found a missconfiguration, there is some usefull commands to fix various situations.

- brctl delbr <bridge> : Deletes a certain bridge. The bridge must be down to perform this action.
- brctl addbr <bridge> : Creates a new empty bridge.
- brctl delif <bridge> <interface> : Remove a certain interface from the bridge.
- brctl addif <bridge> <interface> : Add a certain interface into the bridge.
- vconfig rem <vlan_interface> : Deletes a certain vlan from a certain interface.
- vconfig add <interface> <vlan> : Creates a new vlan interface.