After upgrade VMs getting 1500 MTU although jumbo frame is setup

[Satya Sanjibani Routray]

Steps to recreate the issue

set the jumbo frame on Machine and neutron.conf, ml2.conf and nova.conf

in the ansible code

l3 agent.ini

agent_mode = dvr_snat
network_device_mtu = 9000
{% elif inventory_hostname in groups['compute'] %}
agent_mode = dvr
{% endif %}
{% else %}
agent_mode = legacy

ml2 conf.ini

mechanism_drivers = openvswitch
path_mtu = 9000
{% elif enable_arista_ml2_plugin | bool %}
type_drivers = flat,vlan
tenant_network_types = vlan
{% else %}
# Changing type_drivers after bootstrap can lead to database inconsistencies

neutron.conf

# because it is used by the l3 and dhcp agents. The reason the path has 'kolla'
# in it is because we are sharing this socket in a volume which is it's own dir
metadata_proxy_socket = /var/lib/neutron/kolla/metadata_proxy
global_physnet_mtu = 9000

{% if neutron_plugin_agent == "openvswitch" %}
interface_driver = openvswitch

nova.conf

metadata_listen = {{ api_interface_address }}
metadata_listen_port = {{ nova_metadata_port }}

network_device_mtu = 9000
use_neutron = True
firewall_driver = nova.virt.firewall.NoopFirewallDriver

then deploy using kolla (Ocata almost 3 weeks back)

2. create a VM and verify the VM is having 8950 MTU
3. Upgrade the system to latest version (stable/Ocata)

Observation:
VM is not accessible after upgrade

Reboot the VM

The VM which was created earlier having 1500 MTU where as its tap device is having 8950 MTU and VM is not able to get the IP

Create a New VM
now the new VM is accessible and having MTU as 8950

So after upgrade we will be loosing all the VMs which were created before

[Satya Sanjibani Routray (satroutr)]

After Rebooting the Host able to get the VMs back

but i dont think kolla recommends a reboot of Hosts after upgrade

[Michal Nasiadka (mnasiadka)]

Is this still a problem? If yes - please reproduce on queens/rocky and provide logs.

[Launchpad Janitor (janitor)]

[Expired for kolla because there has been no activity for 60 days.]