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Hi,

On 4/5/23 2:57 AM, Franck VEDEL wrote:
> Hi , and thanks a lot for your help.
> 
> so
> $ sudo ip netns exec qdhcp-8db375e0-28d2-4379-9330-397dc9b4f2b1 ip a
> 3401: tap1c220d25-b9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 68qdisc 
> noqueue state UNKNOWN group default qlen 1000
>      link/ether fa:16:3e:20:ef:bc brd ff:ff:ff:ff:ff:ff
>      inet 169.254.169.254/32 brd 169.254.169.254 scope global tap1c220d25-b9
>         valid_lft forever preferred_lft forever
>      inet 10.1.42.1/24 brd 10.1.42.255 scope global tap1c220d25-b9
>         valid_lft forever preferred_lft forever

Ok, so it is as I thought, someone has set a very small mtu on a network.

> $tail -f /var/log/kolla/neutron/neutron-dhcp-agent.log |grep 
> 8db375e0-28d2-4379-9330-397dc9b4f2b1
> 2023-04-05 08:36:11.558 7 INFO neutron.agent.dhcp.agent [-] Starting 
> network 8db375e0-28d2-4379-9330-397dc9b4f2b1 dhcp configuration
> 2023-04-05 08:36:12.532 7 ERROR neutron.agent.dhcp.agent [-] Unable to 
> enable dhcp for 8db375e0-28d2-4379-9330-397dc9b4f2b1.: 
> neutron.privileged.agent.linux.ip_lib.InvalidArgument: Invalid 
> parameter/value used on interface tap1c220d25-b9, namespace 
> qdhcp-8db375e0-28d2-4379-9330-397dc9b4f2b1.
> 2023-04-05 08:36:12.532 7 ERROR neutron.agent.dhcp.agent 
> neutron.privileged.agent.linux.ip_lib.InvalidArgument: Invalid 
> parameter/value used on interface tap1c220d25-b9, namespace 
> qdhcp-8db375e0-28d2-4379-9330-397dc9b4f2b1.
> 2023-04-05 08:36:12.534 7 INFO neutron.agent.dhcp.agent [-] Finished 
> network 8db375e0-28d2-4379-9330-397dc9b4f2b1 dhcp configuration
> 
> openstack network show 8db375e0-28d2-4379-9330-397dc9b4f2b1
> +---------------------------+--------------------------------------+
> | Field                     | Value                                |
> +---------------------------+--------------------------------------+
> | admin_state_up            | UP                                   |
> | availability_zone_hints   |                                      |
> | availability_zones        | nova                                 |
> | created_at                | 2023-04-04T11:49:47Z                 |
> | description               |                                      |
> | dns_domain                | None                                 |
> | id                        | 8db375e0-28d2-4379-9330-397dc9b4f2b1 |
> | ipv4_address_scope        | None                                 |
> | ipv6_address_scope        | None                                 |
> | is_default                | None                                 |
> | is_vlan_transparent       | None                                 |
> | mtu                       |68                               |
> | name                      | NET1                                 |
> | port_security_enabled     | True                                 |
> | project_id                | 6d6cbcbb6e8d4264bcd13dd8b3d79466     |
> | provider:network_type     | vxlan                                |
> | provider:physical_network | None                                 |
> | provider:segmentation_id  | 456                                  |
> | qos_policy_id             | None                                 |
> | revision_number           | 2                                    |
> | router:external           | Internal                             |
> | segments                  | None                                 |
> | shared                    | False                                |
> | status                    | ACTIVE                               |
> | subnets                   |b72cf65c-1a22-4165-a55b-884bcc9c636a|
> | tags                      |                                      |
> | updated_at                | 2023-04-04T11:49:47Z                 |
> +---------------------------+———————————————————+

Increasing the mtu on this network to at least 1280 should fix the issue 
with DHCP, that is the IPv6 minimum mtu and most likely causing the 
issue. You should check other networks and use the same value, but it is 
probably 1450 given the overlay is vxlan.

Since this is a known issue, there is no need for a new bug, but for 
your reference you can go to https://bugs.launchpad.net/neutron to 
search and file a new one.

Thanks,

-Brian


> 
> $openstack subnet showb72cf65c-1a22-4165-a55b-884bcc9c636a
> +----------------------+--------------------------------------+
> | Field                | Value                                |
> +----------------------+--------------------------------------+
> | allocation_pools     | 10.1.42.1-10.1.42.253                |
> | cidr                 | 10.1.42.0/24                         |
> | created_at           | 2023-04-04T11:49:47Z                 |
> | description          |                                      |
> | dns_nameservers      |                                      |
> | dns_publish_fixed_ip | None                                 |
> | enable_dhcp          | True                                 |
> | gateway_ip           | 10.1.42.254                          |
> | host_routes          |                                      |
> | id                   | b72cf65c-1a22-4165-a55b-884bcc9c636a |
> | ip_version           | 4                                    |
> | ipv6_address_mode    | None                                 |
> | ipv6_ra_mode         | None                                 |
> | name                 |                                      |
> | network_id           | 8db375e0-28d2-4379-9330-397dc9b4f2b1 |
> | project_id           | 6d6cbcbb6e8d4264bcd13dd8b3d79466     |
> | revision_number      | 0                                    |
> | segment_id           | None                                 |
> | service_types        |                                      |
> | subnetpool_id        | None                                 |
> | tags                 |                                      |
> | updated_at           | 2023-04-04T11:49:47Z                 |
> +----------------------+--------------------------------------+
> 
> 
> Since yesterday, we have a lot of network (2 per students , 100 
> students) , so a lot of errors:
> In the log of dnsmask we can see this:
> Apr  5 08:55:02 dnsmasq-dhcp[2466928]: read 
> /var/lib/neutron/dhcp/7d33855e-03a8-431b-9cf8-64f8e95b8f93/host
> Apr  5 08:55:02 dnsmasq-dhcp[2466928]: read 
> /var/lib/neutron/dhcp/7d33855e-03a8-431b-9cf8-64f8e95b8f93/opts
> Apr  5 08:55:05 dnsmasq-dhcp[609053]: DHCPDISCOVER(tap5af0e639-f3) 
> fa:16:3e:8d:86:b9 no address available
> Apr  5 08:55:05 dnsmasq-dhcp[4572]: DHCPDISCOVER(tap6fe70972-c9) 
> fa:16:3e:6d:dc:c8 no address available
> 
> 
> You say: If that's not it please file a new bug with all the above info 
> provided.
> How can I do that ?
> 
> Thanks a lot
> 
> Franck
> 
> 
> 
> 
>> Le 5 avr. 2023 à 00:00, Brian Haley <haleyb.dev at gmail.com 
>> <mailto:haleyb.dev at gmail.com>> a écrit :
>>
>> 8db375e0-28d2-4379-9330-397dc9b4f2b1
>