Creating KVM network bridge on ODA - Not able to connect to database anymore.

A lot of people are using Oracles KVM solution on ODA (Oracle Database Appliance). My company e.g. runs something like application servers in a Linux VM on the ODA lite models for our own software solutions (like communication server, etc.) if a customer runs ODAs (we call it "Solution-in-a-Box"). But there are also other customers, where we just act as system integrator, who want to use KVM on the ODA.

There is a really nice blog how to enable and use KVM on ODA, the starting point is this blog post by Tammy: kvm-on-oda.

It is straight forward, but one of the things are a little bit crucial. It is how to make the network configuration for the KVM on ODA. The best solution is to BRIDGE the network. Ruggero has written a blog post as part of Tammys blog, how you can enable all the different network types.
Don't use NAT or MacVTap - just follow the configuration steps for "Bridged networking (aka "shared physical device")".

Be sure you have access to the iloms host redirection function, because if there is any misconfiguration with the bridge, you lose the network connectivity und you are not able to connect internal (like you could do with ODA HA).

If you have followed the configuration steps and if you can connect to the ODA host again with the bridge configuration, you are not able to connect to the database(s) on that host anymore. Why? Because one mandatory step is missing at Ruggeros example: The configuration of the clusterware (as grid user)! Some tried to stop and start the listener, but the listener will not be started and errors out.

What you need to do as a last configuration step is to modify your clusterware network configuration. The listener is bound to Network 1, which can easily seen by issueing

$ srvctl config listener
Name: LISTENER
Type: Database Listener
Network: 1, Owner: grid
Home: <CRS home>
End points: TCP:1521
Listener is enabled.
Listener is individually enabled on nodes:
Listener is individually disabled on nodes:

To check the configuration, run the following command:
$ srvctl config network
Network 1 exists
Subnet IPv4: 10.214.0.0/255.255.248.0/btbond1, static
Subnet IPv6:
Ping Targets:
Network is enabled
Network is individually enabled on nodes:
Network is individually disabled on nodes:

As you can see, the network is still configured to btbond1 instead of pubbr0.
The syntax (I use the same subnet in my example as Ruggero in his blog) to change this is:
$ srvctl modify network -netnum 1 -subnet 10.214.0.0/255.255.248.0/pubbr0 

Now it is best to either restart the ODA to check if everything is running fine also after an reboot or at least to restart the listener.
$ srvctl stop listener
$ srvctl start listener

Then you are done folks, you can use the bridged device now for your KVM and the databases are reachable again.