Learning SDN

fanoflq · 04-21-2017, 09:09 PM

I am creating a bridge and a port (ethX) like so:

Code:

~$ sudo ovs-vsctl add-br br0
~$ sudo ovs-vsctl list-br 
br0
~$ sudo ovs-vsctl show
96ece70a-9932-4b25-a238-fafec223e4d7
    Bridge "br0"
        Port "br0"
            Interface "br0"
                type: internal
    ovs_version: "2.5.0"
~$ sudo ovs-vsctl add-port br0 ethX
ovs-vsctl: Error detected while setting up 'ethX'.  See ovs-vswitchd log for details.

Here is the log:

Code:

$ tail /var/log/openvswitch/ovs-vswitchd.log
... 
.... ... 
2017-04-22T01:46:28.358Z|00034|bridge|INFO|bridge br0: added interface br0 on port 65534
2017-04-22T01:46:28.358Z|00035|bridge|INFO|bridge br0: using datapath ID 0000b298c24dcc47
2017-04-22T01:46:28.358Z|00036|connmgr|INFO|br0: added service controller "punix:/var/run/openvswitch/br0.mgmt"
2017-04-22T01:47:23.129Z|00037|bridge|WARN|could not open network device ethX (No such device)

It is obvious the port does not exists yet,
until I added it.
Does the error message means I have to create a file of some kind for ethX?
There is no mention of such file for port (ethX) in man ovs-vsctl.
How do I remove this error?

lazydog · 04-21-2017, 10:22 PM

Quote:

Originally Posted by fanoflq

'ethX'

Code:

2017-04-22T01:47:23.129Z|00037|bridge|WARN|could not open network device ethX (No such device)

Run

Code:

ifconfig -a

to see what interfaces you have on your system.

fanoflq · 04-21-2017, 10:32 PM

@lazydog:

i tried this and it works:

Quote:

~$ sudo ovs-vsctl add-port br0 ens3

~$ sudo ovs-vsctl show
96ece70a-9932-4b25-a238-fafec223e4d7
Bridge "br0"
Port "ens3"
Interface "ens3"
Port "br0"
Interface "br0"
type: internal

Then I tried to add a tap and got error:

Quote:

ovs_version: "2.5.0"
~$ ovs-vsctl add-port br0 tap0 tag=1
ovs-vsctl: unix:/var/run/openvswitch/db.sock: database connection failed (Permission denied)
~$ sudo ovs-vsctl add-port br0 tap0 tag=1
ovs-vsctl: Error detected while setting up 'tap0'. See ovs-vswitchd log for detail

Here is the log error:

Quote:

~$ tail /var/log/openvswitch/ovs-vswitchd.log
...
... ...
2017-04-22T03:09:35.116Z|00042|bridge|WARN|could not open network device tap0 (No such device)

There is no tap0 from ifconfig -a.

lazydog · 04-21-2017, 10:37 PM

Quote:

Originally Posted by fanoflq

ovs-vsctl: unix:/var/run/openvswitch/db.sock: database connection failed (Permission denied)

Looks like you need to be root to run this command.

fanoflq · 04-21-2017, 11:19 PM

@lazydog:

Sorry, I pasted the incorrect line item.
Here is the correct error in log:

Quote:

2017-04-22T04:07:10.464Z|00019|bridge|WARN|could not open network device tap0 (No such device)

I know what the problem is.
The (physical or virtual) port has to exists first before we can add it to the virtual bridge.
So we need to use ip command to add a link (e.g. interface eth6) and a tuntap before using command ovs-vsctl to add port.
I am just learning and guessing/inferring as I go.
I wish there is a good newbie tutorial online that does not assume you know a lot already....
Have not found one yet...