8:14 a.m.
Hi Devin,
Below is one example of creating dhcp options and associating them with
logical ports using ovn-nbctl commands. Please see the links shared by
Lance for more details.
Lets say you have a network with cidr - 10.0.0.0/24.
One example would be
$ovn-nbctl dhcp-options-create 10.0.0.0/24
Run the command ovn-nbctl dhcp-options-list and store the uuid of it in any
variable (DHCP_UUID)
Now create the dhcp options for this DHCP_UUID just created.
There are 4 dhcp options which needs to be defined (they are mandatory)
- server_id
- server_mac
- router
- lease_time
since you want to add mtu option as well, you can add the dhcp options as
$ovn-nbctl dhcp-options-set-options $DHCP_UUID server_id=10.0.0.1
server_mac=00:00:00:00:00:10 router=10.0.0.1 lease_time=3600 mtu=1400
The above is just an example. You can see the dhcp options set by running
$ovn-nbctl dhcp-options-get-options $DHCP_UUID
The dhcp options defined here have no value unless you associate these
with the logical switch port.
$ovn-nbctl lsp-set-dhcpv4-options $LPORT_NAME $DHCP_UUID
Suppose if you have 3 logical ports - lp1, lp2 and lp3, you can associate
it as
$ovn-nbctl lsp-set-dhcpv4-options lp1 $DHCP_UUID
$ovn-nbctl lsp-set-dhcpv4-options lp2 $DHCP_UUID
$ovn-nbctl lsp-set-dhcpv4-options lp3 $DHCP_UUID
Please let us know if you have any more questions.
You can refer to this blog to get some more inner details of how native
DHCP is supported in ovn -
https://numansiddiqueblog.wordpress.com/2016/08/09/native-dhcp-support-in...
Thanks
Numan
On Mon, Dec 12, 2016 at 7:28 PM, Lance Richardson <lrichard(a)redhat.com>
wrote:
Hi Devin,
This blog posting does a good job of explaining how to configure OVN
DHCP support:
http://blog.spinhirne.com/2016/09/an-introduction-to-ovn-routing.html
The ovn-nb man page lists the DHCP options that can be provided, including
mtu:
http://openvswitch.org/support/dist-docs/
ovn-
nb.5.html <http://openvswitch.org/support/dist-docs/ovn-nb.5.html>
And the ovn-nbctl man page has details about the command-line interface
for setting DHCP options:
http://openvswitch.org/support/dist-docs/ovn-nbctl.8.html
I have very little experience using OVN's DHCP support, I've copied Numan
in case I've left anything out.
Lance
----- Original Message -----
> From: "Marcin Mirecki" <mmirecki(a)redhat.com>
> To: "Devin Acosta" <devin(a)pabstatencio.com>
> Cc: "users" <Users(a)ovirt.org>, "Lance Richardson"
<lrichard(a)redhat.com>
> Sent: Monday, December 12, 2016 4:35:51 AM
> Subject: Re: oVirt / OVN / MTU
>
> Devin,
>
> oVirt does not currently support changing external network mtu from
within
> ovirt (it rather relies on the provider handling this internally).
>
> If you are using OVN DHCP (have subnets defined for a network), you can
> modify the OVN DHCP options directly in the OVN database.
> I have never actually tested this myself, but looking at the OVN
> documentation, it should do the job on the ports.
>
> The standard OVN way to do so is to use the "ovn-vsctl set DHCP_Options
..."
> command.
> (Unfortunately as I am trying it now it tells me that modifying
DHCP_Options
> is not supported)
> Alternatively, you can use the OVS python API (let me know if you need
any
> help on this).
>
> Lance,
> Would changing the dhcp:options:mtu suffice?
> Could you please comment on how to modify the DHCP MTU using the OVN cmd
> line?
>
> Thanks,
> Marcin
>
>
>
> ----- Original Message -----
> > From: "Devin Acosta" <devin(a)pabstatencio.com>
> > To: "Marcin Mirecki" <mmirecki(a)redhat.com>, "users"
<Users(a)ovirt.org>,
> > "Lance Richardson" <lrichard(a)redhat.com>
> > Sent: Monday, December 12, 2016 1:20:59 AM
> > Subject: Fwd: oVirt / OVN / MTU
> >
> > Marcin / Lance,
> >
> > Not sure if the list was working correctly, I couldn't see that my
message
> > below made it to the list. If I need to change the MTU settings for
OVN /
> > OpenVSwitch to something lower than 1500, what is the best way to do
this?
> > We noticed that some instances (ie: Windows 2012R2) are having issues
with
> > the default MTU of 1500, I think there is an issue at the upper
layers, and
> > we can get it to work if we manually set the MTU on the instance to say
> > 1400. Is there an easy way to do this so that any VM's that come up
> > automatically get MTU of 1400?
> >
> > Devin
> >
> > ---------- Forwarded message ----------
> > From: Devin Acosta <devin(a)pabstatencio.com>
> > Date: Fri, Dec 9, 2016 at 2:02 PM
> > Subject: oVirt / OVN / MTU
> > To: users <Users(a)ovirt.org>
> >
> >
> >
> > We are running oVirt 4.0.5 and we have OVN working to provide a Virtual
> > Layer 2 network. We are noticing that because the OVN is using Geneve
and
> > between all the firewalls and networks it crosses we are running into
an
> > MTU issue. What is the best suggested way to lower say the entire OVN
> > network to say MTU of 1400, and also allow for fragmenting packets?
> >
> >
> > --
> >
> > Devin Acosta
> > Red Hat Certified Architect, LinuxStack
> > 602-354-1220 || devin(a)linuxguru.co
> >
> >
> >
> > --
> >
> > Devin Acosta
> > Red Hat Certified Architect, LinuxStack
> > 602-354-1220 || devin(a)linuxguru.co
> >
>