Looks like the physical interface on the host and the virtual interface on the VM are both at the default 1500 MTU.

How can I determine the MTU setting for the physical switches without admin access to them? Or do I need to ask the network team?



On 5/7/2018 2:03 PM, Clint Boggio wrote:
Randy this flaky layer two problem reeks of a possible MTU situation between 
your oVirt switches and your physical switches.

On May 7, 2018, at 3:59 PM, Dominik Holler <dhol...@redhat.com> wrote:

On Mon, 7 May 2018 11:43:51 -0700
"Rue, Randy" <randy...@gmail.com> wrote:

I've sort of had some progress. On Friday I went to the dentist and
when I returned, my VM could ping google.

I don't believe I changed anything Friday morning but I confess I've
been flailing on this for so long I'm not keeping detailed notes on
what I change. And as I'm evaluating oVirt as a possible replacement
for our production xencenter/xenserver systems, I need to know what
was wrong and what fixed it.

I reinstalled the ovirt-engine box and two hosts and started again.
The only change I've made beyond the default is to remove the
no-mac-spoofing filter from the ovirtmgmt vNIC profile so there are
no filters applied. At this point I'm back to an ubuntu LTS server VM
that again, is getting a DHCP IP address, nameserver entries in
resolv.conf, and "route" shows correct local routing for addresses on
the same subnet and the correct gateway for the rest of the world.
The VM is even registering its hostname in our DNS correctly. And I
can ping the static IP of the host the VM is on, but not the subnet
gateway or anything in the real world.

Can you ping the DHCP server?

Two things I haven't mentioned that I haven't seen anything in the
docs about. My ovirt-engine box is on a different subnet than my
hosts, and my hosts are using a bonded pair of physical interfaces
(XOR mode) for their single LAN connection.
Was the bond created before adding the hosts to oVirt, or after adding
the hosts via oVirt web UI?
If the switch requires configuration for the bond, is this applied?
Can you check if the VM can ping the getaway, if you use a simple
Ethernet connection instead of the bond?

Did I miss something in the docs where these are a problem?

Dominik, to answer your thoughts earlier:

* name resolution isn't happening at all, the VM can't reach a DNS
server

* I don't manage the data center network gear but am pretty sure
there's no configuration that blocks traffic. This is supported by my
temporary success on Friday. And we also have other virtualization
hosts (VMWare hosts) in the same subnet, that forward traffic to/from
their VMs just fine.

OK, L3 seems to work now sometimes.

* tcpdump on the host's ovirtmgmt interface is pretty noisy but if I
grep for the ubuntu DDNS name I see a slew of ARP requests. I can see
pings to the host's IP address, and attempts to SSH from the VM to
its host. Any attempt to touch anything past the host shows nothing
on any interface in tcpdump, not a ping to the subnet gateway, not an
SSH attempt, not a DNS query or a ping to known IP address.

The outgoing ARP requests looks like the traffic of the VM is forwarded
to ovirtmgmt.
Do you see ARP reply to the VM?
Maybe the VM fails to get the MAC address of the gateway.

* hot damn, here's a clue! I can ping other oVirt hosts! (by IP only)
I also tried pinging the ovirt-engine box, wasn't surprised when that
failed as the VM would need to reach the gateway to get to the
different subnet.

So it appears that even though I've set up the ovirtmgmt network
using defaults, and it has the "VM Network" option checked, my
logical network is still set to only allow traffic between the VMs
and hosts.

What am I missing?

-randy
_______________________________________________
Users mailing list
Users@ovirt.org
http://lists.ovirt.org/mailman/listinfo/users


_______________________________________________
Users mailing list
Users@ovirt.org
http://lists.ovirt.org/mailman/listinfo/users

Reply via email to