<div dir="ltr"><br><div>Marcin,Numan,Lance:</div><div><br></div><div>I really appreciate all the assistance that you have given me thus far. I wanted to circle back on this topic, even though I sense I know what the answer will be. ;) My Networking team keeps insisting that they want to control DHCP from their side however yet still be able to create virtual Layer 2 networks within oVirt. I understand that it sounds like OVN was never meant for this kind of configuration. In the setup that we currently have going for the most part Linux boxes are working if we set the MTU to be lower around 1400, however with the Windows boxes we are getting very strange behavior, sometimes we have to set the MTU low to as 1000, but then the next day 1200 works. We aren't fully sure if it's just some strange windows issue with the driver or what. </div><div><br></div><div>One question that was asked of me was if OVS/OVN supports like PMTUD, MTU Protocol discovery? Also I'm suspecting if was to configure oVIRT to use Neutron using OVS I would encounter the same issues I have now with the MTU if they are trying to do DHCP from a virtual appliance on the network? </div><div><br></div><div>Any other comments or suggestions that you can provide on this?</div><div><br></div><div>Thanks again.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Dec 12, 2016 at 7:14 AM, Numan Siddique <span dir="ltr"><<a href="mailto:nusiddiq@redhat.com" target="_blank">nusiddiq@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default"><font face="arial, helvetica, sans-serif">Hi Devin,</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">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.</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">Lets say you have a network with cidr - <a href="http://10.0.0.0/24" target="_blank">10.0.0.0/24</a>.<br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">One example would be</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl dhcp-options-create <a href="http://10.0.0.0/24" target="_blank">10.0.0.0/24</a></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">Run the command ovn-nbctl dhcp-options-list and store the uuid of it in any variable (DHCP_UUID)<br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">Now create the dhcp options for this DHCP_UUID just created.</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">There are 4 dhcp options which needs to be defined (they are mandatory)</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"> - server_id</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"> - <span style="color:rgb(0,0,0)">s</span><span style="color:rgb(0,0,0)">e</span><span style="color:rgb(0,0,0)">r</span><span style="color:rgb(0,0,0)">v</span><span style="color:rgb(0,0,0)">e</span><span style="color:rgb(0,0,0)">r</span><span style="color:rgb(0,0,0)">_</span><span style="color:rgb(0,0,0)">m</span><span style="color:rgb(0,0,0)">a</span><span style="color:rgb(0,0,0)">c</span></font></div><div class="gmail_default"><span style="color:rgb(0,0,0)"><font face="arial, helvetica, sans-serif"> - router</font></span></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><span style="color:rgb(0,0,0)"> - </span><span style="color:rgb(0,0,0)">l</span><span style="color:rgb(0,0,0)">e</span><span style="color:rgb(0,0,0)">a</span><span style="color:rgb(0,0,0)">s</span><span style="color:rgb(0,0,0)">e</span><span style="color:rgb(0,0,0)">_</span><span style="color:rgb(0,0,0)">t</span><span style="color:rgb(0,0,0)">i</span><span style="color:rgb(0,0,0)">m</span><span style="color:rgb(0,0,0)">e</span></font></div><div class="gmail_default"><span style="color:rgb(0,0,0)"><font face="arial, helvetica, sans-serif"><br></font></span></div><div class="gmail_default"><span style="color:rgb(0,0,0)"><font face="arial, helvetica, sans-serif">since you want to add mtu option as well, you can add the dhcp options as </font></span></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl dhcp-options-set-options $DHCP_UUID server_id=10.0.0.1 server_mac=00:00:00:00:00:10 router=10.0.0.1 lease_time=3600 mtu=1400</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">The above is just an example. You can see the dhcp options set by running</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl dhcp-options-get-options $DHCP_UUID</font></div><div class="gmail_extra"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_extra"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_extra"><div class="gmail_default"><font face="arial, helvetica, sans-serif">The dhcp options defined here have no value unless you associate these with the logical switch port.</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl lsp-set-dhcpv4-options $LPORT_NAME $DHCP_UUID<br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">Suppose if you have 3 logical ports - lp1, lp2 and lp3, you can associate it as</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl lsp-set-dhcpv4-options lp1 $DHCP_UUID<br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl lsp-set-dhcpv4-options lp2 $DHCP_UUID<br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">$ovn-nbctl lsp-set-dhcpv4-options lp3 $DHCP_UUID<br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">Please let us know if you have any more questions.</font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">You can refer to this blog to get some more inner details of how native DHCP is supported in ovn - <a href="https://numansiddiqueblog.wordpress.com/2016/08/09/native-dhcp-support-in-ovn/" target="_blank">https://numansiddiqueblog.<wbr>wordpress.com/2016/08/09/<wbr>native-dhcp-support-in-ovn/</a></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">Thanks</font></div><span class="HOEnZb"><font color="#888888"><div class="gmail_default"><font face="arial, helvetica, sans-serif">Numan</font></div></font></span><div><div class="h5"><div class="gmail_default"><font face="arial, helvetica, sans-serif"><br></font></div><br><div class="gmail_quote">On Mon, Dec 12, 2016 at 7:28 PM, Lance Richardson <span dir="ltr"><<a href="mailto:lrichard@redhat.com" target="_blank">lrichard@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Devin,<br>
<br>
This blog posting does a good job of explaining how to configure OVN<br>
DHCP support:<br>
<br>
<a href="http://blog.spinhirne.com/2016/09/an-introduction-to-ovn-routing.html" rel="noreferrer" target="_blank">http://blog.spinhirne.com/2016<wbr>/09/an-introduction-to-ovn-<wbr>routing.html</a><br>
<br>
The ovn-nb man page lists the DHCP options that can be provided, including<br>
mtu:<br>
<br>
<a href="http://openvswitch.org/support/dist-docs/ovn-nb.5.html" rel="noreferrer" target="_blank">http://openvswitch.org/support<wbr>/dist-docs/<div class="gmail_default" style="font-family:monospace,monospace;display:inline"></div>ovn-<div class="gmail_default" style="font-family:monospace,monospace;display:inline"></div>nb.5.html</a><br>
<br>
And the ovn-nbctl man page has details about the command-line interface<br>
for setting DHCP options:<br>
<br>
<a href="http://openvswitch.org/support/dist-docs/ovn-nbctl.8.html" rel="noreferrer" target="_blank">http://openvswitch.org/support<wbr>/dist-docs/ovn-nbctl.8.html</a><br>
<br>
I have very little experience using OVN's DHCP support, I've copied Numan<br>
in case I've left anything out.<br>
<br>
Lance<br>
----- Original Message -----<br>
> From: "Marcin Mirecki" <<a href="mailto:mmirecki@redhat.com" target="_blank">mmirecki@redhat.com</a>><br>
> To: "Devin Acosta" <<a href="mailto:devin@pabstatencio.com" target="_blank">devin@pabstatencio.com</a>><br>
> Cc: "users" <<a href="mailto:Users@ovirt.org" target="_blank">Users@ovirt.org</a>>, "Lance Richardson" <<a href="mailto:lrichard@redhat.com" target="_blank">lrichard@redhat.com</a>><br>
> Sent: Monday, December 12, 2016 4:35:51 AM<br>
> Subject: Re: oVirt / OVN / MTU<br>
><br>
> Devin,<br>
><br>
> oVirt does not currently support changing external network mtu from within<br>
> ovirt (it rather relies on the provider handling this internally).<br>
><br>
> If you are using OVN DHCP (have subnets defined for a network), you can<br>
> modify the OVN DHCP options directly in the OVN database.<br>
> I have never actually tested this myself, but looking at the OVN<br>
> documentation, it should do the job on the ports.<br>
><br>
> The standard OVN way to do so is to use the "ovn-vsctl set DHCP_Options ..."<br>
> command.<br>
> (Unfortunately as I am trying it now it tells me that modifying DHCP_Options<br>
> is not supported)<br>
> Alternatively, you can use the OVS python API (let me know if you need any<br>
> help on this).<br>
><br>
> Lance,<br>
> Would changing the dhcp:options:mtu suffice?<br>
> Could you please comment on how to modify the DHCP MTU using the OVN cmd<br>
> line?<br>
><br>
> Thanks,<br>
> Marcin<br>
><br>
><br>
><br>
> ----- Original Message -----<br>
> > From: "Devin Acosta" <<a href="mailto:devin@pabstatencio.com" target="_blank">devin@pabstatencio.com</a>><br>
> > To: "Marcin Mirecki" <<a href="mailto:mmirecki@redhat.com" target="_blank">mmirecki@redhat.com</a>>, "users" <<a href="mailto:Users@ovirt.org" target="_blank">Users@ovirt.org</a>>,<br>
> > "Lance Richardson" <<a href="mailto:lrichard@redhat.com" target="_blank">lrichard@redhat.com</a>><br>
> > Sent: Monday, December 12, 2016 1:20:59 AM<br>
> > Subject: Fwd: oVirt / OVN / MTU<br>
> ><br>
> > Marcin / Lance,<br>
> ><br>
> > Not sure if the list was working correctly, I couldn't see that my message<br>
> > below made it to the list. If I need to change the MTU settings for OVN /<br>
> > OpenVSwitch to something lower than 1500, what is the best way to do this?<br>
> > We noticed that some instances (ie: Windows 2012R2) are having issues with<br>
> > the default MTU of 1500, I think there is an issue at the upper layers, and<br>
> > we can get it to work if we manually set the MTU on the instance to say<br>
> > 1400. Is there an easy way to do this so that any VM's that come up<br>
> > automatically get MTU of 1400?<br>
> ><br>
> > Devin<br>
> ><br>
> > ---------- Forwarded message ----------<br>
> > From: Devin Acosta <<a href="mailto:devin@pabstatencio.com" target="_blank">devin@pabstatencio.com</a>><br>
> > Date: Fri, Dec 9, 2016 at 2:02 PM<br>
> > Subject: oVirt / OVN / MTU<br>
> > To: users <<a href="mailto:Users@ovirt.org" target="_blank">Users@ovirt.org</a>><br>
> ><br>
> ><br>
> ><br>
> > We are running oVirt 4.0.5 and we have OVN working to provide a Virtual<br>
> > Layer 2 network. We are noticing that because the OVN is using Geneve and<br>
> > between all the firewalls and networks it crosses we are running into an<br>
> > MTU issue. What is the best suggested way to lower say the entire OVN<br>
> > network to say MTU of 1400, and also allow for fragmenting packets?<br>
> ><br>
> ><br>
> > --<br>
> ><br>
> > Devin Acosta<br>
> > Red Hat Certified Architect, LinuxStack<br>
> > <a href="tel:(602)%20354-1220" value="+16023541220" target="_blank">602-354-1220</a> || <a href="mailto:devin@linuxguru.co" target="_blank">devin@linuxguru.co</a><br>
> ><br>
> ><br>
> ><br>
> > --<br>
> ><br>
> > Devin Acosta<br>
> > Red Hat Certified Architect, LinuxStack<br>
> > <a href="tel:(602)%20354-1220" value="+16023541220" target="_blank">602-354-1220</a> || <a href="mailto:devin@linuxguru.co" target="_blank">devin@linuxguru.co</a><br>
> ><br>
><br>
</blockquote></div><br></div></div></div></div>
</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><br></div><div>Devin Acosta</div><div>Red Hat Certified Architect, LinuxStack </div><div>602-354-1220 || <a href="mailto:devin@linuxguru.co" target="_blank">devin@linuxguru.co</a></div></div></div>
</div>