[ovirt-users] Confused by logical networks

[Yaniv Kaul]

On Feb 22, 2018 5:26 PM, "Paul-Erik Törrönen" <poltsi at poltsi.fi> wrote:

I'm not sure how the logical networks should work and would appreciate if
someone could shed some light into the matter, I've tried reading the
documentation¹ but have not become any wiser :-/

For the sake of argument, I have two hosts in the same cluster/DC, They
both have 2 network devices each (let's call them eth0 and eth1). On both
hosts the ovirtmgmgt is connected to eth0 and uses the 10.0.0.0/8-network.
Host 1 is 10.0.0.1 and host 2 is 10.0.0.2. All four network devices are
connected to one switch.

Then I create a logical network, mylogic which should be 192.168.1.0/24,
which I assign to eth1 on each host, but define only for host 1 an
ip-address, 192.168.1.1, host 2 has also the network assigned to eth1, but
withouth an ip address.


There's no reason really to assign IPs to hosts on the logical network.
oVirt provides layer 2 (L2) connectivity to VMs. Whatever DHCP, DNS or
gateway is on that network, they'll use. It should not be one of the hosts.
Their interfaces just bridge the VM traffic over to the designated network,
nothing more.
Y.


Next I create vm1 on host 1, give it a single virtual network connection to
mylogic, and configure the guest to use 192.168.1.2 with gw 192.168.1.1.
Obviously I can from the guest ping 192.168.1.1 which is the host address
on the logical network as the guest is running on the same hardware where
the host ip address is defined.

However, and this is where my confusion lies, if I now create another vm,
vm2, on host 2, attach its network device to the mylogic network and
configure it to use 192.168.1.3 with gw 192.168.1.1, I can not ping neither
192.168.1.1 nor 192.168.1.2.

My understanding is that vm2 should be able to ping the wm1 as well as the
gateway address defined on host 1. However this does not seem to be the
case.

What have I missed here?

TIA,

Poltsi

¹ https://www.ovirt.org/documentation/admin-guide/chap-Logical_Networks/
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