Michal, Thank you for your response. Please accept my clarifications below. > On 15.10.2015 20:23, George Trakatelis wrote: > > Hi all, > > > > I want to set the advertised value of MTU for virbr0 interface on a > > Fedora 21 host to 1454 to accommodate the installation of new VMs for > > testing purposes. > > The aforementioned host is an OpenStack VM actually, which explains > > the need for a lower than 1500 MTU. > > > > I noticed Pieter Hollants' patch to set dhcp-option=<number>,"<value>" > > for an interface, but it seems that it has not been implemented yet. I should have written (for the patch) "that it has not been applied yet". Digging further, I realized that it has been applied but pulled before 1.0.3 for a number of reasons as explained by Laine Stump http://www.redhat.com/archives/libvir-list/2013-March/msg00166.html > The patch is in: > > Author: Pieter Hollants <pieter@xxxxxxxxxxxx> > AuthorDate: Thu Feb 21 23:40:17 2013 +0100 > Commit: Laine Stump <laine@xxxxxxxxx> > CommitDate: Fri Feb 22 19:45:19 2013 -0500 > > Add support for <option> tag in network config > > This patch adds support for a new <option>-Tag in the <dhcp> block of > network configs, based on a subset of the fifth proposal by Laine > Stump in the mailing list discussion at > https://www.redhat.com/archives/libvir-list/2012-November/msg01054.html. > > [...] > > But I don't think it will solve your problem. IIUC you want to modify > MTU of virbr0, not just advertise altered MTU to domains. Well, in my case (which I briefly described earlier), having dhcp-option=26,1454 or dhcp-option-force=26,1454 in /var/lib/libvirt/dnsmasq/default.conf does the trick. > Does this virbr0 come from the default libvirt network? > If so, I am afraid there's no way how to specify MTU. > What you could do, is to define <interface/> [1] > and then bridged <network/> [2] that will use the interface. > Libvirt already has support for setting MTUs for host interfaces. > > Michal I'll try that! For the time being, I applied a mini version of the patch. George _______________________________________________ libvirt-users mailing list libvirt-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvirt-users
