Problem Description: Clearly explain the issue.

when neighbor_responder is set as all, arp for lb vip which is not in the same subnet is not replied

 Impact Assessment: Describe the severity and impact (e.g., network down,availability of a workaround, etc.).

 Software Versions: Specify the exact versions in use (e.g.,openvswitch3.1-3.1.0-147.el8fdp).

[root@wsfd-advnetlab18 test]# rpm -qa | grep -E "openvwitch3.3|ovn24.09"
ovn24.09-24.09.1-10.el9fdp.x86_64
ovn24.09-central-24.09.1-10.el9fdp.x86_64
ovn24.09-host-24.09.1-10.el9fdp.x86_64

  Issue Type: Indicate whether this is a new issue or a regression (if a regression, state the last known working version).

 Reproducibility: Confirm if the issue can be reproduced consistently. If not, describe how often it occurs.

100%

 Reproduction Steps: Provide detailed steps or scripts to replicate the issue.

systemctl start openvswitch                          
systemctl start ovn-northd                                                                            
ovn-nbctl set-connection ptcp:6641                                                                    
ovn-sbctl set-connection ptcp:6642
ovs-vsctl set open . external_ids:system-id=hv1 external_ids:ovn-remote=tcp:127.0.0.1:6642 external_ids:ovn-encap-type=geneve external_ids:ovn-encap-ip=127.0.0.1
systemctl restart ovn-controllerovn-nbctl lr-add lr1
ovn-nbctl lrp-add lr1 lr1-ls1 00:00:01:ff:02:03 192.168.1.254/24
ovn-nbctl ls-add ls1
ovn-nbctl lsp-add ls1 ls1p1
ovn-nbctl lsp-set-addresses ls1p1 "00:00:01:01:01:01 192.168.1.1"
ovn-nbctl lsp-add ls1 ls1-lr1
ovn-nbctl lsp-set-type ls1-lr1 router
ovn-nbctl lsp-set-options ls1-lr1 router-port=lr1-ls1
ovn-nbctl lsp-set-addresses ls1-lr1 router
ovn-nbctl set logical_router lr1 options:chassis=hv1
ovn-nbctl lb-add lb1 192.168.1.100 192.168.1.1
ovn-nbctl lr-lb-add lr1 lb1
ovn-nbctl lb-add lb2 172.16.1.1 192.168.1.1
ovn-nbctl lr-lb-add lr1 lb2
ovn-nbctl set load_balancer lb1 options:neighbor_responder=all
ovn-nbctl set load_balancer lb2 options:neighbor_responder=all
ovn-nbctl --wait=hv sync
ovs-vsctl add-port br-int ls1p1 -- set interface ls1p1 type=internal external_ids:iface-id=ls1p1
ip netns add ls1p1
ip link set ls1p1 netns ls1p1
ip netns exec ls1p1 ip link set ls1p1 address 00:00:01:01:01:01
ip netns exec ls1p1 ip link set ls1p1 up
ip netns exec ls1p1 ip addr add 192.168.1.1/24 dev ls1p1
ip netns exec ls1p1 ip route add default via 192.168.1.254
ip netns exec ls1p1 ip route add 172.16.1.1 dev ls1p1
ip netns exec ls1p1 ping 192.168.1.100 -c 1 -w 1 -W 1
ip netns exec ls1p1 ping 172.16.1.1 -c 1 -w 1 -W 1
ip netns exec ls1p1 arping 192.168.1.100 -c 1
ip netns exec ls1p1 arping 172.16.1.1 -c 1 

 Expected Behavior: Describe what should happen under normal circumstances.

arping 172.16.1.1 should receive arp reply

 Observed Behavior: Explain what actually happens.

arping 172.16.1.1 doesn't receive arp reply

 Troubleshooting Actions: Outline the steps taken to diagnose or resolve the issue so far.

 Logs: If you collected logs please provide them (e.g. sos report, /var/log/openvswitch/* , testpmd console)

+ ip netns exec ls1p1 ping 192.168.1.100 -c 1 -w 1 -W 1                                               
PING 192.168.1.100 (192.168.1.100) 56(84) bytes of data.                                              

— 192.168.1.100 ping statistics —                                                                 
1 packets transmitted, 0 received, 100% packet loss, time 0ms                                         
                                                                                                      
+ ip netns exec ls1p1 ping 172.16.1.1 -c 1 -w 1 -W 1                                                  
PING 172.16.1.1 (172.16.1.1) 56(84) bytes of data.                                                    
                                                                                                                                                                                                            
— 172.16.1.1 ping statistics —                                                                                                                                                                          
1 packets transmitted, 0 received, 100% packet loss, time 0ms
                                                                                                                                                                                                            
+ ip netns exec ls1p1 arping 192.168.1.100 -c 1
ARPING 192.168.1.100 from 192.168.1.1 ls1p1
Unicast reply from 192.168.1.100 [00:00:01:FF:02:03]  1.027ms
Sent 1 probes (1 broadcast(s))                                                                        
Received 1 response(s)                             
+ ip netns exec ls1p1 arping 172.16.1.1 -c 1
ARPING 172.16.1.1 from 192.168.1.1 ls1p1
Sent 1 probes (1 broadcast(s))                                                                        
Received 0 response(s)

<=== arp reply is not received