After googling, I found following statement. 

If your deployment has SR-IOV instances, make sure that at least one of the
OVN chassis named applications has the ``prefer-chassis-as-gw`` configuration
option set to 'true'.

But in my older deployment I didn't have the above option and still sriov working fine and receiving DHCP IP automatically. Is this a new option I need to set? 

Currently I have following options

(openvswitch-vswitchd)[root@os-chn-ctrl02 /]# ovs-vsctl list open_vswitch
_uuid               : 773e18f8-b646-4cf2-8da3-2f6ab501f0e3
bridges             : [d398d109-3ca2-4ca2-bb09-3235e329260d, eaeb638c-4cf1-44e5-b4fc-9088574542de]
cur_cfg             : 18
datapath_types      : [netdev, system]
datapaths           : {system=ae76447d-f54e-44f0-aefb-775756b67689}
db_version          : []
dpdk_initialized    : false
dpdk_version        : none
external_ids        : {hostname=os-chn-ctrl02, ovn-bridge-mappings="physnet1:br-ex", ovn-cms-options=enable-chassis-as-gw, ovn-encap-ip="172.16.0.12", ovn-encap-type=geneve, ovn-monitor-all="false", ovn-openflow-probe-interval="60", ovn-remote="tcp:10.74.0.11:6642,tcp:10.74.0.12:6642,tcp:10.74.0.13:6642", ovn-remote-probe-interval="60000", system-id=os-chn-ctrl02}
iface_types         : [afxdp, afxdp-nonpmd, bareudp, erspan, geneve, gre, gtpu, internal, ip6erspan, ip6gre, lisp, patch, srv6, stt, system, tap, vxlan]
manager_options     : []
next_cfg            : 18
other_config        : {ovn-chassis-idx-os-chn-ctrl02="", vlan-limit="0"}
ovs_version         : []
ssl                 : []
statistics          : {}
system_type         : []
system_version      : []

On Sun, Feb 9, 2025 at 12:11 AM Satish Patel <satish.txt@gmail.com> wrote:

Folks,

I have built a new openstack using kolla-ansible with 2024.1 with OVN plugin. So far everything is working good. Today I have added a new compute node with SRIOV port and it turns out vm is not able to obtain IP from DHCP. 

With the same subnet if I create general vm then it works and obtains IP but with sriov port it doesn't work. If I assign IP static on the vm interface then my VM is able to ping the outside world. 

I have deployed many clouds with OVN and SRIOV and never had an issue so I never dig into any kind of troubleshooting. This is the first time I have seen this issue. I have checked port mapping etc and all looks good. 

In SRIOV case what is the flow of DHCP? does physical interface send DHCP request on wire or DHCP request route via OVN br-int bridge? How will handle that DHCP request?

Following two SRIOV port I have created but they are not able to obtain IP address via dhcp

(ovn-nb-db)[root@os-chn-ctrl03 /]# ovn-nbctl --no-leader-only find Logical_Switch_Port type=external
_uuid               : a274df3b-6967-4f73-91ff-8f6eb46f70e0
addresses           : ["fa:16:3e:03:55:44 10.74.2.35"]
dhcpv4_options      : 7829902c-5cdf-49cf-b478-7b683669c726
dhcpv6_options      : []
dynamic_addresses   : []
enabled             : true
external_ids        : {"neutron:cidrs"="10.74.2.35/23", "neutron:device_id"="f4b91945-32f9-4961-a2cf-26b408218e35", "neutron:device_owner"="compute:sriov", "neutron:mtu"="", "neutron:network_name"=neutron-87131346-90d6-48ca-a045-214ff02ee9c0, "neutron:port_capabilities"="rx;tx;sg;tso;gso;gro;rxvlan;txvlan;rxhash;txudptnl", "neutron:port_name"=my-sriov-port, "neutron:project_id"="0c4956dce56a4503878007355850a04a", "neutron:revision_number"="32", "neutron:security_group_ids"="0bd505e8-d086-4d72-8e56-b913a8672f08", "neutron:subnet_pool_addr_scope4"="", "neutron:subnet_pool_addr_scope6"="", "neutron:vnic_type"=direct}
ha_chassis_group    : 0c41026b-3b01-485e-908a-523202aefcf9
mirror_rules        : []
name                : "0cbe012e-902a-4503-91a2-191b5f4acac5"
options             : {}
parent_name         : []
port_security       : ["fa:16:3e:03:55:44 10.74.2.35"]
tag                 : []
tag_request         : []
type                : external
up                  : true

_uuid               : 1b245b6d-b720-41cd-a09c-79dc7eab3149
addresses           : ["fa:16:3e:d8:4b:ab 10.74.2.181"]
dhcpv4_options      : 7829902c-5cdf-49cf-b478-7b683669c726
dhcpv6_options      : []
dynamic_addresses   : []
enabled             : true
external_ids        : {"neutron:cidrs"="10.74.2.181/23", "neutron:device_id"="ac767d12-cff0-484e-b014-f3e42160cd8c", "neutron:device_owner"="compute:sriov", "neutron:mtu"="", "neutron:network_name"=neutron-87131346-90d6-48ca-a045-214ff02ee9c0, "neutron:port_capabilities"="rx;tx;sg;tso;gso;gro;rxvlan;txvlan;rxhash;txudptnl", "neutron:port_name"=my-sriov-p1, "neutron:project_id"="0c4956dce56a4503878007355850a04a", "neutron:revision_number"="5", "neutron:security_group_ids"="0bd505e8-d086-4d72-8e56-b913a8672f08", "neutron:subnet_pool_addr_scope4"="", "neutron:subnet_pool_addr_scope6"="", "neutron:vnic_type"=direct}
ha_chassis_group    : 0c41026b-3b01-485e-908a-523202aefcf9
mirror_rules        : []
name                : "bdf9261c-5cfc-4df1-9c11-c8ec26535eef"
options             : {}
parent_name         : []
port_security       : ["fa:16:3e:d8:4b:ab 10.74.2.181"]
tag                 : []
tag_request         : []
type                : external
up                  : true