Mailing List Archive

How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers)
Hi all,

I'm running Openstack Ocata (Deployed with openstack-ansible), with the
following configuration:

* Compute nodesrunning nova and neutron agent
* 2 x Controllersrunning neutronserver/agents in LXC containers (as
deployed by openstack-ansible playbooks)
* Underlying hosts have a single NIC (MTU 9000) with multiple VLAN
subinterafces, which in turn are connected to bridges br-vxlan, br-vlan,
br-management


I've encountered the following problem:

1. When I create in instance in a vxlan tenant network, without changing
any configuration files, the instance (linux default) assumes an MTU of
1500, but in reality only has an MTU of 1450 (because of the VXLAN
overhead). Instances cannot ping each other or their gateway (a neutron
router) with > 1450 MTU.

2. While I _could_ push an MTU of 1450 to my instances via DHCP, this is
(a) not always reliable depending on the guest OS, and (b) breaks
dockeron instances, which defaults to an MTU of 1500 for docker0

3. So, I attempted the configuration changes described at
http://serverascode.com/2017/06/06/neutron-vxlan-tenant-mtu-1500.html,
increasing my global MTU to 1550 in neutron.conf / ml2_conf.ini, on the
compute nodes, and the neutron client & server LXC containers on the
controller, so that a default MTU of 1500 in my instances would always work.

4. The effect of step #3 above is that now my instances can communicate
with _each other_ at up to 1500 MTU, _but_ they still can't ping their
gateway (the neutron router) at anything over 1450 MTU.

5. When I examine my compute nodes (underlying host OS), I note that the
bridge "br-vxlan" contains the vlan subinterface (MTU 9000) plus a veth
interface for connectivity to the neutron-agents LXC container (e.g.
"04063403_eth10"). The veth interface has an MTU of 1500. The
corresponding interface within the neutron-agents LXC container (eth10)
also has an MTU of 1500.

6. Assuming that #5 is the cause of my MTU fault (i.e., a 1500-byte
packet from the instance over the tentant network = 1500+50=1550, can't
pass through the veth interface), I manually changed the veth interface
(and the corresponding interface within the LXC container) to MTU 1550.

7. Now I can pass packets from my instances to the neutron router as
large as 1468 bytes (previous limit was 1448), but still not the 1500
bytes I expected.

8. Increasing the MTU again (per #6 above) to 1600 makes no difference
to the result in #7 above.


So, I'm thinking I've missed something, and the most likely issue is the
definition of the LXC container (and veth interfaces) for neutron-agents
on the controller. I thought it was a simple fix (manually change MTU
per #6), but I'm baffled re why increasing MTU on the veth interfaces by
50 bytes only got me 20 bytes more overhead (1468), and even if this
_was_ the fix, it's obviously only temporary, so I wonder what is the
correct way to address the MTU issue under openstack-ansible?

Can anybody shed some light on this?

Thanks!
David
Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
Hello,

Thanks for the reply, responses inline below:

> Hello,
>
> I haven't touched this for a while, but could you give us your user_*
> variable overrides?

OK, here we go. Let me know if there’s a preferred way to send large
data blocks - I considered a gist or a pastebin, but figured that having
the content archived with the mailing list message would be the best result.

I think the overrides is what you’re asking for? The only MTU-related
override I have is “container/mtu” for the vxlan network below. I expect
it doesn’t actually _do/ anything though, because I can’t find the
string “container_mtu” within any of the related ansible roles (see grep
for container_mtu vs container_bridge below for illustration). I found
https://bugs.launchpad.net/openstack-ansible/+bug/1678165 which looked
related

|root@nbs-dh-09:~# grep container_mtu /etc/ansible/ -ri root@nbs-dh-09:~#
grep container_bridge /etc/ansible/ -ri
/etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
"br-mgmt" /etc/ansible/roles/plugins/library/provider_networks:#
container_bridge: "br-vxlan"
/etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
"br-vlan" /etc/ansible/roles/plugins/library/provider_networks:#
container_bridge: "br-vlan"
/etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
"br-storage" /etc/ansible/roles/plugins/library/provider_networks:
bind_device = net['network']['container_bridge']
/etc/ansible/roles/os_neutron/doc/source/configure-network-services.rst:
container_bridge: "br-vlan" root@nbs-dh-09:~# |

|global_overrides: internal_lb_vip_address: 10.76.76.11 # # The below
domain name must resolve to an IP address # in the CIDR specified in
haproxy_keepalived_external_vip_cidr. # If using different protocols
(https/http) for the public/internal # endpoints the two addresses must
be different. # external_lb_vip_address: openstack.dev.safenz.net
tunnel_bridge: "br-vxlan" management_bridge: "br-mgmt"
provider_networks: - network: container_bridge: "br-mgmt"
container_type: "veth" container_interface: "eth1" ip_from_q:
"container" type: "raw" group_binds: - all_containers - hosts
is_container_address: true is_ssh_address: true - network:
container_bridge: "br-vxlan" container_type: "veth" container_interface:
"eth10" container_mtu: "9000" ip_from_q: "tunnel" type: "vxlan" range:
"1:1000" net_name: "vxlan" group_binds: - neutron_linuxbridge_agent -
network: container_bridge: "br-vlan" container_type: "veth"
container_interface: "eth12" host_bind_override: "eth12" type: "flat"
net_name: "flat" group_binds: - neutron_linuxbridge_agent - network:
container_bridge: "br-vlan" container_type: "veth" container_interface:
"eth11" type: "vlan" range: "1:4094" net_name: "vlan" group_binds: -
neutron_linuxbridge_agent - network: container_bridge: "br-storage"
container_type: "veth" container_interface: "eth2" ip_from_q: "storage"
type: "raw" group_binds: - glance_api - cinder_api - cinder_volume -
nova_compute - swift_proxy |

> Here are a few things I watch for mtu related discussions:
> 1) ``lxc_net_mtu``: It is used in lxc_hosts to define the lxc bridge.

Aha. I didn’t know about this, it sounds like what I need. I’ll add this
and report back.

> 2) Your compute nodes and your controller nodes need to have
> consistent mtus on their bridges.

They are both configured for an MTU of 9000, but the controller nodes
bridges’ drop their MTU to 1500 when the veth interface paired with the
neutron-agent LXC container is joined to the bridge (bridges downgrade
their MTU to the MTU of the lowest participating interface)

> 3) Neutron needs a configuration override.

I’ve set this in neutron.conf on all neutron LXC containers, and on the
compute nodes too:
|global_physnet_mtu = 1550|

And likewise in /etc/neutron/plugins/ml2/ml2_conf.ini:

|# Set a global MTU of 1550 (to allow VXLAN at 1500) path_mtu = 1550 #
Drop VLAN and FLAT providers back to 1500, to align with outside FWs
physical_network_mtus = vlan:1500,flat:1500 |

> 4) the lxc containers need to be properly defined: each network should
> have a mtu defined, or alternatively, you can define a default mtu for
> all the networks defined in openstack_user_config with
> ``lxc_container_default_mtu``. (This one is the one that spawns up the
> veth pair to the lxc container)

I didn’t know about this one either, it didn’t exist in any of the
default ansible-provided sample configs, but now that I’ve grepped in
the ansible roles for “mtu”, it’s obvious. I’ll try this too.

|root@nbs-dh-09:~# grep -ri lxc_container_default_mtu
/etc/openstack_deploy/* root@nbs-dh-09:~# grep -ri
lxc_container_default_mtu /etc/ansible/
/etc/ansible/roles/lxc_container_create/defaults/main.yml:lxc_container_default_mtu:
"1500"
/etc/ansible/roles/lxc_container_create/templates/container-interface.ini.j2:lxc.network.mtu
= {{ item.value.mtu|default(lxc_container_default_mtu) }}
/etc/ansible/roles/lxc_container_create/templates/debian-interface.cfg.j2:
mtu {{ item.value.mtu|default(lxc_container_default_mtu) }}
/etc/ansible/roles/lxc_container_create/templates/rhel-interface.j2:MTU={{
item.value.mtu|default(lxc_container_default_mtu) }} root@nbs-dh-09:~# |

> 5) The container interfaces need to have this proper mtu. This is
> taking the same configuration as 4) above, so it should work out of
> the box.

Agreed, that seems to be the case currently with 1500, I’d expect it to
be true with the updated value

> 6) If your instance is reaching its router with no mtu issue, you may
> still have issues for the Northbound trafic. Check how you configured
> this northbound and if the interfaces have proper mtu. If there are
> veth pairs to create pseudo links, check their mtus too.
>
> I think it's a good start for the conversation...

Thank you, this is very helpful. I’ll give it a try and respond.

Re #1 and #4, do I need to destroy / recreate my existing LXC
containers, or will rerunning the playbooks be enough to update the MTUs?

Many thanks,
David

?
Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
An update to my reply below..

I’ve realized that I need a per-network MTU defined in
/etc/openstack_deploy/openstack_user_config.yml, so I’ve done the following:

|global_overrides: <snip> provider_networks: - network: container_bridge:
"br-mgmt" <snip> container_mtu: "1500" <snip> - network:
container_bridge: "br-vxlan" container_mtu: "1550" type: "vxlan" <snip>
- network: container_bridge: "br-vlan" type: "flat" net_name: "flat"
container_mtu: "1500" <snip> - network: container_bridge: "br-vlan"
type: "vlan" container_mtu: "1500" <snip> - network: container_bridge:
"br-storage" type: "raw" container_mtu: "9000" group_binds: - glance_api
- cinder_api - cinder_volume - nova_compute - swift_proxy |

I think that gets me:

* VXLAN LXC interfaces will have an MTU of 1550 (necessary for “raw”
1500 from the instances)
* flat/vlan interfaces will have an MTU of 1500 (let’s be consistent)
* storage interfaces can have an MTU of 9000

Then, I set the following in /etc/openstack_deploy/user_variables.yml:

|lxc_net_mtu: 1550 lxc_container_default_mtu: 1550 |

I don’t know whether this is redundant or not based on the above, but it
seemed sensible.

I’m rerunning the setup-everything.yml playbook, but still not sure
whether the changes apply if there’s an existing LXC container defined.
We’ll find out soon enough…

Cheers,
D

On 06/12/2017 21:51, David Young wrote:

> Hello,
>
> Thanks for the reply, responses inline below:
>
>> Hello,
>>
>> I haven't touched this for a while, but could you give us your user_*
>> variable overrides?
>
> OK, here we go. Let me know if there’s a preferred way to send large
> data blocks - I considered a gist or a pastebin, but figured that
> having the content archived with the mailing list message would be the
> best result.
>
> I think the overrides is what you’re asking for? The only MTU-related
> override I have is “container/mtu” for the vxlan network below. I
> expect it doesn’t actually _do/ anything though, because I can’t find
> the string “container_mtu” within any of the related ansible roles
> (see grep for container_mtu vs container_bridge below for
> illustration). I found
> https://bugs.launchpad.net/openstack-ansible/+bug/1678165 which looked
> related
>
> |root@nbs-dh-09:~# grep container_mtu /etc/ansible/ -ri
> root@nbs-dh-09:~# grep container_bridge /etc/ansible/ -ri
> /etc/ansible/roles/plugins/library/provider_networks:#
> container_bridge: "br-mgmt"
> /etc/ansible/roles/plugins/library/provider_networks:#
> container_bridge: "br-vxlan"
> /etc/ansible/roles/plugins/library/provider_networks:#
> container_bridge: "br-vlan"
> /etc/ansible/roles/plugins/library/provider_networks:#
> container_bridge: "br-vlan"
> /etc/ansible/roles/plugins/library/provider_networks:#
> container_bridge: "br-storage"
> /etc/ansible/roles/plugins/library/provider_networks: bind_device =
> net['network']['container_bridge']
> /etc/ansible/roles/os_neutron/doc/source/configure-network-services.rst:
> container_bridge: "br-vlan" root@nbs-dh-09:~# |
> |global_overrides: internal_lb_vip_address: 10.76.76.11 # # The below
> domain name must resolve to an IP address # in the CIDR specified in
> haproxy_keepalived_external_vip_cidr. # If using different protocols
> (https/http) for the public/internal # endpoints the two addresses
> must be different. # external_lb_vip_address: openstack.dev.safenz.net
> tunnel_bridge: "br-vxlan" management_bridge: "br-mgmt"
> provider_networks: - network: container_bridge: "br-mgmt"
> container_type: "veth" container_interface: "eth1" ip_from_q:
> "container" type: "raw" group_binds: - all_containers - hosts
> is_container_address: true is_ssh_address: true - network:
> container_bridge: "br-vxlan" container_type: "veth"
> container_interface: "eth10" container_mtu: "9000" ip_from_q: "tunnel"
> type: "vxlan" range: "1:1000" net_name: "vxlan" group_binds: -
> neutron_linuxbridge_agent - network: container_bridge: "br-vlan"
> container_type: "veth" container_interface: "eth12"
> host_bind_override: "eth12" type: "flat" net_name: "flat" group_binds:
> - neutron_linuxbridge_agent - network: container_bridge: "br-vlan"
> container_type: "veth" container_interface: "eth11" type: "vlan"
> range: "1:4094" net_name: "vlan" group_binds: -
> neutron_linuxbridge_agent - network: container_bridge: "br-storage"
> container_type: "veth" container_interface: "eth2" ip_from_q:
> "storage" type: "raw" group_binds: - glance_api - cinder_api -
> cinder_volume - nova_compute - swift_proxy |
>> Here are a few things I watch for mtu related discussions:
>> 1) ``lxc_net_mtu``: It is used in lxc_hosts to define the lxc bridge.
>
> Aha. I didn’t know about this, it sounds like what I need. I’ll add
> this and report back.
>
>> 2) Your compute nodes and your controller nodes need to have
>> consistent mtus on their bridges.
>
> They are both configured for an MTU of 9000, but the controller nodes
> bridges’ drop their MTU to 1500 when the veth interface paired with
> the neutron-agent LXC container is joined to the bridge (bridges
> downgrade their MTU to the MTU of the lowest participating interface)
>
>> 3) Neutron needs a configuration override.
>
> I’ve set this in neutron.conf on all neutron LXC containers, and on
> the compute nodes too:
> |global_physnet_mtu = 1550|
>
> And likewise in /etc/neutron/plugins/ml2/ml2_conf.ini:
>
> |# Set a global MTU of 1550 (to allow VXLAN at 1500) path_mtu = 1550 #
> Drop VLAN and FLAT providers back to 1500, to align with outside FWs
> physical_network_mtus = vlan:1500,flat:1500 |
>> 4) the lxc containers need to be properly defined: each network should
>> have a mtu defined, or alternatively, you can define a default mtu for
>> all the networks defined in openstack_user_config with
>> ``lxc_container_default_mtu``. (This one is the one that spawns up the
>> veth pair to the lxc container)
>
> I didn’t know about this one either, it didn’t exist in any of the
> default ansible-provided sample configs, but now that I’ve grepped in
> the ansible roles for “mtu”, it’s obvious. I’ll try this too.
>
> |root@nbs-dh-09:~# grep -ri lxc_container_default_mtu
> /etc/openstack_deploy/* root@nbs-dh-09:~# grep -ri
> lxc_container_default_mtu /etc/ansible/
> /etc/ansible/roles/lxc_container_create/defaults/main.yml:lxc_container_default_mtu:
> "1500"
> /etc/ansible/roles/lxc_container_create/templates/container-interface.ini.j2:lxc.network.mtu
> = {{ item.value.mtu|default(lxc_container_default_mtu) }}
> /etc/ansible/roles/lxc_container_create/templates/debian-interface.cfg.j2:
> mtu {{ item.value.mtu|default(lxc_container_default_mtu) }}
> /etc/ansible/roles/lxc_container_create/templates/rhel-interface.j2:MTU={{
> item.value.mtu|default(lxc_container_default_mtu) }} root@nbs-dh-09:~# |
>> 5) The container interfaces need to have this proper mtu. This is
>> taking the same configuration as 4) above, so it should work out of
>> the box.
>
> Agreed, that seems to be the case currently with 1500, I’d expect it
> to be true with the updated value
>
>> 6) If your instance is reaching its router with no mtu issue, you may
>> still have issues for the Northbound trafic. Check how you configured
>> this northbound and if the interfaces have proper mtu. If there are
>> veth pairs to create pseudo links, check their mtus too.
>>
>> I think it's a good start for the conversation...
>
> Thank you, this is very helpful. I’ll give it a try and respond.
>
> Re #1 and #4, do I need to destroy / recreate my existing LXC
> containers, or will rerunning the playbooks be enough to update the MTUs?
>
> Many thanks,
> David
>
> ?

?
Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
On 6 December 2017 at 09:09, David Young <davidy@funkypenguin.co.nz> wrote:
> An update to my reply below..
>
> I’ve realized that I need a per-network MTU defined in
> /etc/openstack_deploy/openstack_user_config.yml, so I’ve done the following:
>
> global_overrides:
> <snip>
> provider_networks:
> - network:
> container_bridge: "br-mgmt"
> <snip>
> container_mtu: "1500"
> <snip>
> - network:
> container_bridge: "br-vxlan"
> container_mtu: "1550"
> type: "vxlan"
> <snip>
> - network:
> container_bridge: "br-vlan"
> type: "flat"
> net_name: "flat"
> container_mtu: "1500"
> <snip>
> - network:
> container_bridge: "br-vlan"
> type: "vlan"
> container_mtu: "1500"
> <snip>
> - network:
> container_bridge: "br-storage"
> type: "raw"
> container_mtu: "9000"
> group_binds:
> - glance_api
> - cinder_api
> - cinder_volume
> - nova_compute
> - swift_proxy
>
> I think that gets me:
>
> VXLAN LXC interfaces will have an MTU of 1550 (necessary for “raw” 1500 from
> the instances)
> flat/vlan interfaces will have an MTU of 1500 (let’s be consistent)
> storage interfaces can have an MTU of 9000
>
> Then, I set the following in /etc/openstack_deploy/user_variables.yml:
>
> lxc_net_mtu: 1550
> lxc_container_default_mtu: 1550
>
> I don’t know whether this is redundant or not based on the above, but it
> seemed sensible.
>
> I’m rerunning the setup-everything.yml playbook, but still not sure whether
> the changes apply if there’s an existing LXC container defined. We’ll find
> out soon enough…
>
> Cheers,
> D
>
> On 06/12/2017 21:51, David Young wrote:
>
> Hello,
>
> Thanks for the reply, responses inline below:
>
> Hello,
>
> I haven't touched this for a while, but could you give us your user_*
> variable overrides?
>
> OK, here we go. Let me know if there’s a preferred way to send large data
> blocks - I considered a gist or a pastebin, but figured that having the
> content archived with the mailing list message would be the best result.
>
> I think the overrides is what you’re asking for? The only MTU-related
> override I have is “containermtu” for the vxlan network below. I expect it
> doesn’t actually _do anything though, because I can’t find the string
> “container_mtu” within any of the related ansible roles (see grep for
> container_mtu vs container_bridge below for illustration). I found
> https://bugs.launchpad.net/openstack-ansible/+bug/1678165 which looked
> related
>
> root@nbs-dh-09:~# grep container_mtu /etc/ansible/ -ri
> root@nbs-dh-09:~# grep container_bridge /etc/ansible/ -ri
> /etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
> "br-mgmt"
> /etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
> "br-vxlan"
> /etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
> "br-vlan"
> /etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
> "br-vlan"
> /etc/ansible/roles/plugins/library/provider_networks:# container_bridge:
> "br-storage"
> /etc/ansible/roles/plugins/library/provider_networks:
> bind_device = net['network']['container_bridge']
> /etc/ansible/roles/os_neutron/doc/source/configure-network-services.rst:
> container_bridge: "br-vlan"
> root@nbs-dh-09:~#
>
> global_overrides:
> internal_lb_vip_address: 10.76.76.11
> #
> # The below domain name must resolve to an IP address
> # in the CIDR specified in haproxy_keepalived_external_vip_cidr.
> # If using different protocols (https/http) for the public/internal
> # endpoints the two addresses must be different.
> #
> external_lb_vip_address: openstack.dev.safenz.net
> tunnel_bridge: "br-vxlan"
> management_bridge: "br-mgmt"
> provider_networks:
> - network:
> container_bridge: "br-mgmt"
> container_type: "veth"
> container_interface: "eth1"
> ip_from_q: "container"
> type: "raw"
> group_binds:
> - all_containers
> - hosts
> is_container_address: true
> is_ssh_address: true
> - network:
> container_bridge: "br-vxlan"
> container_type: "veth"
> container_interface: "eth10"
> container_mtu: "9000"
> ip_from_q: "tunnel"
> type: "vxlan"
> range: "1:1000"
> net_name: "vxlan"
> group_binds:
> - neutron_linuxbridge_agent
> - network:
> container_bridge: "br-vlan"
> container_type: "veth"
> container_interface: "eth12"
> host_bind_override: "eth12"
> type: "flat"
> net_name: "flat"
> group_binds:
> - neutron_linuxbridge_agent
> - network:
> container_bridge: "br-vlan"
> container_type: "veth"
> container_interface: "eth11"
> type: "vlan"
> range: "1:4094"
> net_name: "vlan"
> group_binds:
> - neutron_linuxbridge_agent
> - network:
> container_bridge: "br-storage"
> container_type: "veth"
> container_interface: "eth2"
> ip_from_q: "storage"
> type: "raw"
> group_binds:
> - glance_api
> - cinder_api
> - cinder_volume
> - nova_compute
> - swift_proxy
>
> Here are a few things I watch for mtu related discussions:
> 1) ``lxc_net_mtu``: It is used in lxc_hosts to define the lxc bridge.
>
> Aha. I didn’t know about this, it sounds like what I need. I’ll add this and
> report back.
>
> 2) Your compute nodes and your controller nodes need to have
> consistent mtus on their bridges.
>
> They are both configured for an MTU of 9000, but the controller nodes
> bridges’ drop their MTU to 1500 when the veth interface paired with the
> neutron-agent LXC container is joined to the bridge (bridges downgrade their
> MTU to the MTU of the lowest participating interface)
>
> 3) Neutron needs a configuration override.
>
> I’ve set this in neutron.conf on all neutron LXC containers, and on the
> compute nodes too:
> global_physnet_mtu = 1550
>
> And likewise in /etc/neutron/plugins/ml2/ml2_conf.ini:
>
> # Set a global MTU of 1550 (to allow VXLAN at 1500)
> path_mtu = 1550
>
> # Drop VLAN and FLAT providers back to 1500, to align with outside FWs
> physical_network_mtus = vlan:1500,flat:1500
>
> 4) the lxc containers need to be properly defined: each network should
> have a mtu defined, or alternatively, you can define a default mtu for
> all the networks defined in openstack_user_config with
> ``lxc_container_default_mtu``. (This one is the one that spawns up the
> veth pair to the lxc container)
>
> I didn’t know about this one either, it didn’t exist in any of the default
> ansible-provided sample configs, but now that I’ve grepped in the ansible
> roles for “mtu”, it’s obvious. I’ll try this too.
>
> root@nbs-dh-09:~# grep -ri lxc_container_default_mtu /etc/openstack_deploy/*
> root@nbs-dh-09:~# grep -ri lxc_container_default_mtu /etc/ansible/
> /etc/ansible/roles/lxc_container_create/defaults/main.yml:lxc_container_default_mtu:
> "1500"
> /etc/ansible/roles/lxc_container_create/templates/container-interface.ini.j2:lxc.network.mtu
> = {{ item.value.mtu|default(lxc_container_default_mtu) }}
> /etc/ansible/roles/lxc_container_create/templates/debian-interface.cfg.j2:
> mtu {{ item.value.mtu|default(lxc_container_default_mtu) }}
> /etc/ansible/roles/lxc_container_create/templates/rhel-interface.j2:MTU={{
> item.value.mtu|default(lxc_container_default_mtu) }}
> root@nbs-dh-09:~#
>
> 5) The container interfaces need to have this proper mtu. This is
> taking the same configuration as 4) above, so it should work out of
> the box.
>
> Agreed, that seems to be the case currently with 1500, I’d expect it to be
> true with the updated value
>
> 6) If your instance is reaching its router with no mtu issue, you may
> still have issues for the Northbound trafic. Check how you configured
> this northbound and if the interfaces have proper mtu. If there are
> veth pairs to create pseudo links, check their mtus too.
>
> I think it's a good start for the conversation...
>
> Thank you, this is very helpful. I’ll give it a try and respond.
>
> Re #1 and #4, do I need to destroy / recreate my existing LXC containers, or
> will rerunning the playbooks be enough to update the MTUs?
>
> Many thanks,
> David


Hello,

For the mtu, it would be impactful to do it on a live environment. I
expect that if you change the container configuration, it would
restart.

Could you please tell me if this configuration was good enough for
your use case?
Or if the docs need adapting?

If this still doesn't work, maybe you should file a bug with your new
openstack_user_config
and the appropriate user_*.yml file. That would follow our bug triage
process where more ppl can have a look at the issue.

As usual, don't hesitate to come on our irc channel #openstack-ansible
if you have further questions!

Thank you!

Best regards,
Jean-Philippe Evrard
@evrardjp

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Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
So..

On 07/12/2017 03:12, Jean-Philippe Evrard wrote:

> For the mtu, it would be impactful to do it on a live environment. I
> expect that if you change the container configuration, it would
> restart.

It’s a busy lab environment, but given that it’s fully HA (2
controllers), I didn’t anticipate a significant problem with changing
container configuration one-at-a-time.

However, the change has had an unexpected side effect - one of the
controllers (I haven’t rebooted the other one yet) seems to have lost
the ability to bring up lxcbr0, and so while it can start all its
containers, none of them have any management connectivity on eth0, which
of course breaks all sorts of things.

I.e.

|root@nbs-dh-10:~# systemctl status networking.service ?
networking.service - Raise network interfaces Loaded: loaded
(/lib/systemd/system/networking.service; enabled; vendor preset:
enabled) Drop-In: /run/systemd/generator/networking.service.d
??50-insserv.conf-$network.conf Active: failed (Result: exit-code) since
Thu 2017-12-07 06:37:00 NZDT; 14min ago Docs: man:interfaces(5) Process:
2717 ExecStart=/sbin/ifup -a --read-environment (code=exited,
status=1/FAILURE) Process: 2656 ExecStartPre=/bin/sh -c [
"$CONFIGURE_INTERFACES" != "no" ] && [ -n "$(ifquery --read-environment
--list --exclude=lo)" ] && udevadm settle (code=e Main PID: 2717
(code=exited, status=1/FAILURE) Dec 07 06:36:58 nbs-dh-10 systemd[1]:
Starting Raise network interfaces... Dec 07 06:36:58 nbs-dh-10
ifup[2717]: RTNETLINK answers: Invalid argument Dec 07 06:36:58
nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
/run/network/ifstate.enp4s0 Dec 07 06:36:58 nbs-dh-10 ifup[2717]:
/sbin/ifup: waiting for lock on /run/network/ifstate.br-mgmt Dec 07
06:37:00 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
/run/network/ifstate.br-vlan Dec 07 06:37:00 nbs-dh-10 ifup[2717]:
Failed to bring up lxcbr0. Dec 07 06:37:00 nbs-dh-10 systemd[1]:
networking.service: Main process exited, code=exited, status=1/FAILURE
Dec 07 06:37:00 nbs-dh-10 systemd[1]: Failed to start Raise network
interfaces. Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service:
Unit entered failed state. Dec 07 06:37:00 nbs-dh-10 systemd[1]:
networking.service: Failed with result 'exit-code'. root@nbs-dh-10:~# |

I’ve manually reversed the “lxc.network.mtu = 1550” entry in
/etc/lxc/lxc-openstack.conf, but this doesn’t seem to have made a
difference.

What’s also odd is that lxcbr0 appears to be perfectly normal:

|root@nbs-dh-10:~# brctl show lxcbr0 bridge name bridge id STP enabled
interfaces lxcbr0 8000.fe0a7fa28303 no 04063403_eth0 075266dc_eth0
160c9b30_eth0 38ac19ae_eth0 4f57300f_eth0 59b2b5a5_eth0 5b7bbeb4_eth0
64a1fcdd_eth0 6c99f5fe_eth0 6f93ebb2_eth0 70ce61e5_eth0 745ba80d_eth0
85df2fa5_eth0 99e6adf8_eth0 cbdfa2f3_eth0 e15dc279_eth0 ea67ce7e_eth0
ed5c7af9_eth0 root@nbs-dh-10:~# |

… But, no matter the value of lxc.network.mtu, it doesn’t change from
1500 (I suppose this could actually have reduced itself based on the
lower MTUs of the member interfaces though):

|root@nbs-dh-10:~# ifconfig lxcbr0 lxcbr0 Link encap:Ethernet HWaddr
fe:0c:5d:1c:36:da inet addr:10.0.3.1 Bcast:10.0.3.255 Mask:255.255.255.0
inet6 addr: fe80::f4b0:bff:fec3:63b0/64 Scope:Link UP BROADCAST RUNNING
MULTICAST MTU:1500 Metric:1 RX packets:499 errors:0 dropped:0 overruns:0
frame:0 TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000 RX bytes:128882 (128.8 KB) TX bytes:828
(828.0 B) root@nbs-dh-10:~# |

Any debugging suggestions?

Thanks,
D

?
Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
Hello David,

Did you solve your issue?
Did you check that it depends on the default container interface's mtu itself?

Best regards,
JP


On 6 December 2017 at 18:45, David Young <davidy@funkypenguin.co.nz> wrote:
> So..
>
> On 07/12/2017 03:12, Jean-Philippe Evrard wrote:
>
> For the mtu, it would be impactful to do it on a live environment. I
> expect that if you change the container configuration, it would
> restart.
>
> It’s a busy lab environment, but given that it’s fully HA (2 controllers), I
> didn’t anticipate a significant problem with changing container
> configuration one-at-a-time.
>
> However, the change has had an unexpected side effect - one of the
> controllers (I haven’t rebooted the other one yet) seems to have lost the
> ability to bring up lxcbr0, and so while it can start all its containers,
> none of them have any management connectivity on eth0, which of course
> breaks all sorts of things.
>
> I.e.
>
> root@nbs-dh-10:~# systemctl status networking.service
> ? networking.service - Raise network interfaces
> Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor
> preset: enabled)
> Drop-In: /run/systemd/generator/networking.service.d
> ??50-insserv.conf-$network.conf
> Active: failed (Result: exit-code) since Thu 2017-12-07 06:37:00 NZDT;
> 14min ago
> Docs: man:interfaces(5)
> Process: 2717 ExecStart=/sbin/ifup -a --read-environment (code=exited,
> status=1/FAILURE)
> Process: 2656 ExecStartPre=/bin/sh -c [ "$CONFIGURE_INTERFACES" != "no" ]
> && [ -n "$(ifquery --read-environment --list --exclude=lo)" ] && udevadm
> settle (code=e
> Main PID: 2717 (code=exited, status=1/FAILURE)
>
> Dec 07 06:36:58 nbs-dh-10 systemd[1]: Starting Raise network interfaces...
> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: RTNETLINK answers: Invalid argument
> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
> /run/network/ifstate.enp4s0
> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
> /run/network/ifstate.br-mgmt
> Dec 07 06:37:00 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
> /run/network/ifstate.br-vlan
> Dec 07 06:37:00 nbs-dh-10 ifup[2717]: Failed to bring up lxcbr0.
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Main process
> exited, code=exited, status=1/FAILURE
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: Failed to start Raise network
> interfaces.
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Unit entered
> failed state.
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Failed with result
> 'exit-code'.
> root@nbs-dh-10:~#
>
> I’ve manually reversed the “lxc.network.mtu = 1550” entry in
> /etc/lxc/lxc-openstack.conf, but this doesn’t seem to have made a
> difference.
>
> What’s also odd is that lxcbr0 appears to be perfectly normal:
>
> root@nbs-dh-10:~# brctl show lxcbr0
> bridge name bridge id STP enabled interfaces
> lxcbr0 8000.fe0a7fa28303 no 04063403_eth0
> 075266dc_eth0
> 160c9b30_eth0
> 38ac19ae_eth0
> 4f57300f_eth0
> 59b2b5a5_eth0
> 5b7bbeb4_eth0
> 64a1fcdd_eth0
> 6c99f5fe_eth0
> 6f93ebb2_eth0
> 70ce61e5_eth0
> 745ba80d_eth0
> 85df2fa5_eth0
> 99e6adf8_eth0
> cbdfa2f3_eth0
> e15dc279_eth0
> ea67ce7e_eth0
> ed5c7af9_eth0
> root@nbs-dh-10:~#
>
> … But, no matter the value of lxc.network.mtu, it doesn’t change from 1500
> (I suppose this could actually have reduced itself based on the lower MTUs
> of the member interfaces though):
>
> root@nbs-dh-10:~# ifconfig lxcbr0
> lxcbr0 Link encap:Ethernet HWaddr fe:0c:5d:1c:36:da
> inet addr:10.0.3.1 Bcast:10.0.3.255 Mask:255.255.255.0
> inet6 addr: fe80::f4b0:bff:fec3:63b0/64 Scope:Link
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:499 errors:0 dropped:0 overruns:0 frame:0
> TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000
> RX bytes:128882 (128.8 KB) TX bytes:828 (828.0 B)
>
> root@nbs-dh-10:~#
>
> Any debugging suggestions?
>
> Thanks,
> D

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Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
Hey Jean-Philippe,

No, after I disasterously split-brained/partitioned my rabbitmq and
galera clusters by allowing LXC to start the containers up without the
dnsmasq process to address their eth0 interfaces (due to what _may_ be a
template/Xenial bug), I've spent the last few days cleaning upthe mess:)

I have twounused hosts set aside as a test environment for pre-testing,
and I'll be leveraging these in the next few days to test theissue on a
fresh Xenial install.

I'll update you (and the list) once I've positively confirmed the issue.

Cheers!
D




On 12/12/2017 21:52, Jean-Philippe Evrard wrote:
> Hello David,
>
> Did you solve your issue?
> Did you check that it depends on the default container interface's mtu itself?
>
> Best regards,
> JP
>
>
> On 6 December 2017 at 18:45, David Young <davidy@funkypenguin.co.nz> wrote:
>> So..
>>
>> On 07/12/2017 03:12, Jean-Philippe Evrard wrote:
>>
>> For the mtu, it would be impactful to do it on a live environment. I
>> expect that if you change the container configuration, it would
>> restart.
>>
>> It’s a busy lab environment, but given that it’s fully HA (2 controllers), I
>> didn’t anticipate a significant problem with changing container
>> configuration one-at-a-time.
>>
>> However, the change has had an unexpected side effect - one of the
>> controllers (I haven’t rebooted the other one yet) seems to have lost the
>> ability to bring up lxcbr0, and so while it can start all its containers,
>> none of them have any management connectivity on eth0, which of course
>> breaks all sorts of things.
>>
>> I.e.
>>
>> root@nbs-dh-10:~# systemctl status networking.service
>> ? networking.service - Raise network interfaces
>> Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor
>> preset: enabled)
>> Drop-In: /run/systemd/generator/networking.service.d
>> ??50-insserv.conf-$network.conf
>> Active: failed (Result: exit-code) since Thu 2017-12-07 06:37:00 NZDT;
>> 14min ago
>> Docs: man:interfaces(5)
>> Process: 2717 ExecStart=/sbin/ifup -a --read-environment (code=exited,
>> status=1/FAILURE)
>> Process: 2656 ExecStartPre=/bin/sh -c [ "$CONFIGURE_INTERFACES" != "no" ]
>> && [ -n "$(ifquery --read-environment --list --exclude=lo)" ] && udevadm
>> settle (code=e
>> Main PID: 2717 (code=exited, status=1/FAILURE)
>>
>> Dec 07 06:36:58 nbs-dh-10 systemd[1]: Starting Raise network interfaces...
>> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: RTNETLINK answers: Invalid argument
>> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
>> /run/network/ifstate.enp4s0
>> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
>> /run/network/ifstate.br-mgmt
>> Dec 07 06:37:00 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
>> /run/network/ifstate.br-vlan
>> Dec 07 06:37:00 nbs-dh-10 ifup[2717]: Failed to bring up lxcbr0.
>> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Main process
>> exited, code=exited, status=1/FAILURE
>> Dec 07 06:37:00 nbs-dh-10 systemd[1]: Failed to start Raise network
>> interfaces.
>> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Unit entered
>> failed state.
>> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Failed with result
>> 'exit-code'.
>> root@nbs-dh-10:~#
>>
>> I’ve manually reversed the “lxc.network.mtu = 1550” entry in
>> /etc/lxc/lxc-openstack.conf, but this doesn’t seem to have made a
>> difference.
>>
>> What’s also odd is that lxcbr0 appears to be perfectly normal:
>>
>> root@nbs-dh-10:~# brctl show lxcbr0
>> bridge name bridge id STP enabled interfaces
>> lxcbr0 8000.fe0a7fa28303 no 04063403_eth0
>> 075266dc_eth0
>> 160c9b30_eth0
>> 38ac19ae_eth0
>> 4f57300f_eth0
>> 59b2b5a5_eth0
>> 5b7bbeb4_eth0
>> 64a1fcdd_eth0
>> 6c99f5fe_eth0
>> 6f93ebb2_eth0
>> 70ce61e5_eth0
>> 745ba80d_eth0
>> 85df2fa5_eth0
>> 99e6adf8_eth0
>> cbdfa2f3_eth0
>> e15dc279_eth0
>> ea67ce7e_eth0
>> ed5c7af9_eth0
>> root@nbs-dh-10:~#
>>
>> … But, no matter the value of lxc.network.mtu, it doesn’t change from 1500
>> (I suppose this could actually have reduced itself based on the lower MTUs
>> of the member interfaces though):
>>
>> root@nbs-dh-10:~# ifconfig lxcbr0
>> lxcbr0 Link encap:Ethernet HWaddr fe:0c:5d:1c:36:da
>> inet addr:10.0.3.1 Bcast:10.0.3.255 Mask:255.255.255.0
>> inet6 addr: fe80::f4b0:bff:fec3:63b0/64 Scope:Link
>> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
>> RX packets:499 errors:0 dropped:0 overruns:0 frame:0
>> TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
>> collisions:0 txqueuelen:1000
>> RX bytes:128882 (128.8 KB) TX bytes:828 (828.0 B)
>>
>> root@nbs-dh-10:~#
>>
>> Any debugging suggestions?
>>
>> Thanks,
>> D
Re: How to deal with MTU issue on routers servicing vxlan tenant networks? (openstack-ansible with LXC containers) [ In reply to ]
Hello,

Ok thanks! Don't hesitate to ask on our channel.

FYI: In case of split brains for rabbitmq, most likely recreating
rabbit is the fastest. We are dealing with non persistent data anyway
:p

Best regards,
JP

On 12 December 2017 at 09:20, David Young <davidy@funkypenguin.co.nz> wrote:
> Hey Jean-Philippe,
>
> No, after I disasterously split-brained/partitioned my rabbitmq and galera
> clusters by allowing LXC to start the containers up without the dnsmasq
> process to address their eth0 interfaces (due to what _may_ be a
> template/Xenial bug), I've spent the last few days cleaning up the mess :)
>
> I have two unused hosts set aside as a test environment for pre-testing, and
> I'll be leveraging these in the next few days to test the issue on a fresh
> Xenial install.
>
> I'll update you (and the list) once I've positively confirmed the issue.
>
> Cheers!
> D
>
>
>
>
> On 12/12/2017 21:52, Jean-Philippe Evrard wrote:
>
> Hello David,
>
> Did you solve your issue?
> Did you check that it depends on the default container interface's mtu
> itself?
>
> Best regards,
> JP
>
>
> On 6 December 2017 at 18:45, David Young <davidy@funkypenguin.co.nz> wrote:
>
> So..
>
> On 07/12/2017 03:12, Jean-Philippe Evrard wrote:
>
> For the mtu, it would be impactful to do it on a live environment. I
> expect that if you change the container configuration, it would
> restart.
>
> It’s a busy lab environment, but given that it’s fully HA (2 controllers), I
> didn’t anticipate a significant problem with changing container
> configuration one-at-a-time.
>
> However, the change has had an unexpected side effect - one of the
> controllers (I haven’t rebooted the other one yet) seems to have lost the
> ability to bring up lxcbr0, and so while it can start all its containers,
> none of them have any management connectivity on eth0, which of course
> breaks all sorts of things.
>
> I.e.
>
> root@nbs-dh-10:~# systemctl status networking.service
> ? networking.service - Raise network interfaces
> Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor
> preset: enabled)
> Drop-In: /run/systemd/generator/networking.service.d
> ??50-insserv.conf-$network.conf
> Active: failed (Result: exit-code) since Thu 2017-12-07 06:37:00 NZDT;
> 14min ago
> Docs: man:interfaces(5)
> Process: 2717 ExecStart=/sbin/ifup -a --read-environment (code=exited,
> status=1/FAILURE)
> Process: 2656 ExecStartPre=/bin/sh -c [ "$CONFIGURE_INTERFACES" != "no" ]
> && [ -n "$(ifquery --read-environment --list --exclude=lo)" ] && udevadm
> settle (code=e
> Main PID: 2717 (code=exited, status=1/FAILURE)
>
> Dec 07 06:36:58 nbs-dh-10 systemd[1]: Starting Raise network interfaces...
> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: RTNETLINK answers: Invalid argument
> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
> /run/network/ifstate.enp4s0
> Dec 07 06:36:58 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
> /run/network/ifstate.br-mgmt
> Dec 07 06:37:00 nbs-dh-10 ifup[2717]: /sbin/ifup: waiting for lock on
> /run/network/ifstate.br-vlan
> Dec 07 06:37:00 nbs-dh-10 ifup[2717]: Failed to bring up lxcbr0.
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Main process
> exited, code=exited, status=1/FAILURE
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: Failed to start Raise network
> interfaces.
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Unit entered
> failed state.
> Dec 07 06:37:00 nbs-dh-10 systemd[1]: networking.service: Failed with result
> 'exit-code'.
> root@nbs-dh-10:~#
>
> I’ve manually reversed the “lxc.network.mtu = 1550” entry in
> /etc/lxc/lxc-openstack.conf, but this doesn’t seem to have made a
> difference.
>
> What’s also odd is that lxcbr0 appears to be perfectly normal:
>
> root@nbs-dh-10:~# brctl show lxcbr0
> bridge name bridge id STP enabled interfaces
> lxcbr0 8000.fe0a7fa28303 no 04063403_eth0
> 075266dc_eth0
> 160c9b30_eth0
> 38ac19ae_eth0
> 4f57300f_eth0
> 59b2b5a5_eth0
> 5b7bbeb4_eth0
> 64a1fcdd_eth0
> 6c99f5fe_eth0
> 6f93ebb2_eth0
> 70ce61e5_eth0
> 745ba80d_eth0
> 85df2fa5_eth0
> 99e6adf8_eth0
> cbdfa2f3_eth0
> e15dc279_eth0
> ea67ce7e_eth0
> ed5c7af9_eth0
> root@nbs-dh-10:~#
>
> … But, no matter the value of lxc.network.mtu, it doesn’t change from 1500
> (I suppose this could actually have reduced itself based on the lower MTUs
> of the member interfaces though):
>
> root@nbs-dh-10:~# ifconfig lxcbr0
> lxcbr0 Link encap:Ethernet HWaddr fe:0c:5d:1c:36:da
> inet addr:10.0.3.1 Bcast:10.0.3.255 Mask:255.255.255.0
> inet6 addr: fe80::f4b0:bff:fec3:63b0/64 Scope:Link
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:499 errors:0 dropped:0 overruns:0 frame:0
> TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000
> RX bytes:128882 (128.8 KB) TX bytes:828 (828.0 B)
>
> root@nbs-dh-10:~#
>
> Any debugging suggestions?
>
> Thanks,
> D
>
>

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