libvirt users - Mar 2018 - Re: Specify DNS and gateway for dnsmasq

Hi all,
how I can set dhcp options as DNS, gateway, etc in libvirt's network 
definitions?

 From what I read here[1], I can use the <option> tag. However, I can 
not find nothing on libvirt official documentation.

I am missing something?
Thanks.

[1] https://www.redhat.com/archives/libvir-list/2013-March/msg00166.html

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8

On 03/12/2018 06:45 PM, Gionatan Danti wrote:
> Hi all,
> how I can set dhcp options as DNS, gateway, etc in libvirt's network
> definitions?
The default GW depends on the IP address you assigned to your network:

<ip address='192.168.122.1' netmask='255.255.255.0'/>

This says the default GW is 192.168.122.1/24. However, you can insert
other routes too:

<route address="192.168.222.0" prefix="24"
gateway="192.168.122.2"/>

For handling DNS, you need to focus on <dns/> element. For instance, to
set a different forwarder than GW:

<dns>
  <forwarder addr="8.8.8.8"/>
</dns>

It's all documented here:

https://libvirt.org/formatnetwork.html#elementsStaticroute

and in the subsequent section.

> 
> From what I read here[1], I can use the <option> tag. However, I can
not
> find nothing on libvirt official documentation.
No, that was just a proposal. RFC, a discussion how should we implement
some special features of DHCP. Those are not patches and in fact patches
implementing that were never merged.

Michal

On 13/03/2018 15:30, Michal Privoznik wrote:> The default GW depends on 
the IP address you assigned to your network:
> 
> <ip address='192.168.122.1' netmask='255.255.255.0'/>
> 
> This says the default GW is 192.168.122.1/24. However, you can insert
> other routes too:
> 
> <route address="192.168.222.0" prefix="24"
gateway="192.168.122.2"/>
> 
> For handling DNS, you need to focus on <dns/> element. For instance,
to
> set a different forwarder than GW:
> 
> <dns>
>    <forwarder addr="8.8.8.8"/>
> </dns>
For NATed/routed networks, sure. However, I have an isolated network 
like that (without the "forward" element):

<network>
   <name>net1</name>
   <uuid>dcf5c09b-dcb6-4fd3-86b8-6312a7b94bf6</uuid>
   <bridge name='virbr1' stp='on' delay='0'/>
   <mac address='52:54:00:97:1b:15'/>
   <domain name='TEST'/>
   <ip address='192.168.10.1' netmask='255.255.255.0'>
     <dhcp>
       <range start='192.168.10.128'
end='192.168.10.254'/>
     </dhcp>
   </ip>
</network>

When the client asks for an IP via DHCP, it obtain a valid IP address 
but *no* gateway. Is it the expected behavior for an isolated network? 
 From my understanding, network isolation is accomplished by firewall 
rules in the FORWARD table, rather than by not assigning the gateway IP 
address to clients.
> 
> No, that was just a proposal. RFC, a discussion how should we implement
> some special features of DHCP. Those are not patches and in fact patches
> implementing that were never merged.
> 
> Michal
> 
Ok, thank you Michal.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8