SOLVED:
The problem was solved by changing Bond Mode from Balance-rr to Active-Backup.

------------------------
Good afternoon,
I have set up a ProxMox server for the first time, and everything has gone well so far.
My network: 192.168.12.1/24
VM: Windows Server 2025
The configuration on ProxMox can be found in the screenshot.
2 interfaces (eno1 & eno2), Linux bond (bond0) and Linux bridge (bond0).
I can ping outside with my ProxMox host.
When I connect a VM to the bridge, assign it an IP address, and ping 1.1.1.1 or 192.168.12.1, it doesn't work.
When I ping the host, it works.
The qemu agent is installed (see screenshot).
What am I doing wrong?
Kind Regards,
EDIT:
The ARP requests originate from the VM (192.168.12.15)
The ARP replies are returned correctly from the gateway (192.168.12.1)
However, Windows responds as if it is not receiving or does not trust those ARP replies
root@LS-PVE-00:~# tcpdump -i vmbr1 arp or icmp
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on vmbr1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
11:38:25.462096 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:25.462150 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:25.462215 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:26.460865 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:26.460914 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:26.461106 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:26.690047 ARP, Request who-has 192.168.12.50 (Broadcast) tell 192.168.12.50, length 46
11:38:26.690054 ARP, Request who-has 192.168.12.50 (Broadcast) tell 192.168.12.50, length 46
11:38:27.461369 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:27.461424 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:27.461628 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:28.522668 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:28.522717 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:28.522936 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:29.460658 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:29.460706 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:29.460797 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:30.461181 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:30.461220 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:30.461448 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:30.465167 ARP, Request who-has LS-PVE-00.datawolk.cloud (2c:ea:7f:50:09:ce (oui Unknown)) tell 192.168.12.100, length 46
11:38:30.465173 ARP, Reply LS-PVE-00.datawolk.cloud is-at 2c:ea:7f:50:09:ce (oui Unknown), length 28
11:38:30.576428 ARP, Request who-has 192.168.12.100 tell LS-PVE-00.datawolk.cloud, length 28
11:38:30.576987 ARP, Reply 192.168.12.100 is-at 00:15:5d:0c:fb:00 (oui Unknown), length 46
11:38:32.522895 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:32.522939 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:32.523225 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:33.461990 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:33.462038 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:33.462128 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:34.460722 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:34.460770 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:34.460948 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:36.533384 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:36.533427 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:36.533631 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:37.462320 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:37.462363 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:37.462550 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:38.462190 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:38.462252 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:38.462413 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:39.678062 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:39.678107 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:39.678310 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:40.461487 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:40.461533 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:40.461738 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:41.461939 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:41.461978 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:41.462084 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:44.463828 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:44.463882 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:44.464097 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:45.460830 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:45.460892 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:45.461057 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:46.461317 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:46.461371 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:46.461586 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:49.003356 ARP, Request who-has 192.168.12.1 (Broadcast) tell 192.168.12.150, length 46
11:38:49.003361 ARP, Request who-has 192.168.12.1 (Broadcast) tell 192.168.12.150, length 46
11:38:49.464434 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:49.464473 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:49.464723 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
^C
65 packets captured
65 packets received by filter
0 packets dropped by kernel
EDIT 2:
Broadcom Gigabit Ethernet BCM5720
Intel(R) Gigabit 4P I350-t Adapter
root@LS-PVE-00:~# lspci -k | grep -A 3 -i ethernet
04:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720 Gigabit Ethernet PCIe
DeviceName: NIC1
Subsystem: Dell NetXtreme BCM5720 Gigabit Ethernet PCIe
Kernel driver in use: tg3
Kernel modules: tg3
04:00.1 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720 Gigabit Ethernet PCIe
DeviceName: NIC2
Subsystem: Dell NetXtreme BCM5720 Gigabit Ethernet PCIe
Kernel driver in use: tg3
Kernel modules: tg3
17:02.0 PCI bridge: Intel Corporation Sky Lake-E PCI Express Root Port C (rev 04)
pcilib: Error reading /sys/bus/pci/devices/0000:18:00.0/label: Operation not permitted
--
3b:00.0 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
3b:00.1 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
3b:00.2 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
3b:00.3 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
5d:05.0 System peripheral: Intel Corporation Sky Lake-E VT-d (rev 04)
The problem was solved by changing Bond Mode from Balance-rr to Active-Backup.

------------------------
Good afternoon,
I have set up a ProxMox server for the first time, and everything has gone well so far.
My network: 192.168.12.1/24
VM: Windows Server 2025
The configuration on ProxMox can be found in the screenshot.
2 interfaces (eno1 & eno2), Linux bond (bond0) and Linux bridge (bond0).
I can ping outside with my ProxMox host.
When I connect a VM to the bridge, assign it an IP address, and ping 1.1.1.1 or 192.168.12.1, it doesn't work.
When I ping the host, it works.
The qemu agent is installed (see screenshot).
What am I doing wrong?

Kind Regards,
EDIT:



root@LS-PVE-00:~# tcpdump -i vmbr1 arp or icmp
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on vmbr1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
11:38:25.462096 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:25.462150 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:25.462215 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:26.460865 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:26.460914 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:26.461106 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:26.690047 ARP, Request who-has 192.168.12.50 (Broadcast) tell 192.168.12.50, length 46
11:38:26.690054 ARP, Request who-has 192.168.12.50 (Broadcast) tell 192.168.12.50, length 46
11:38:27.461369 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:27.461424 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:27.461628 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:28.522668 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:28.522717 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:28.522936 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:29.460658 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:29.460706 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:29.460797 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:30.461181 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:30.461220 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:30.461448 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:30.465167 ARP, Request who-has LS-PVE-00.datawolk.cloud (2c:ea:7f:50:09:ce (oui Unknown)) tell 192.168.12.100, length 46
11:38:30.465173 ARP, Reply LS-PVE-00.datawolk.cloud is-at 2c:ea:7f:50:09:ce (oui Unknown), length 28
11:38:30.576428 ARP, Request who-has 192.168.12.100 tell LS-PVE-00.datawolk.cloud, length 28
11:38:30.576987 ARP, Reply 192.168.12.100 is-at 00:15:5d:0c:fb:00 (oui Unknown), length 46
11:38:32.522895 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:32.522939 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:32.523225 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:33.461990 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:33.462038 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:33.462128 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:34.460722 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:34.460770 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:34.460948 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:36.533384 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:36.533427 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:36.533631 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:37.462320 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:37.462363 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:37.462550 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:38.462190 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:38.462252 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:38.462413 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:39.678062 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:39.678107 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:39.678310 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:40.461487 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:40.461533 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:40.461738 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:41.461939 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:41.461978 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:41.462084 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:44.463828 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:44.463882 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:44.464097 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:45.460830 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:45.460892 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:45.461057 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:46.461317 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:46.461371 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:46.461586 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
11:38:49.003356 ARP, Request who-has 192.168.12.1 (Broadcast) tell 192.168.12.150, length 46
11:38:49.003361 ARP, Request who-has 192.168.12.1 (Broadcast) tell 192.168.12.150, length 46
11:38:49.464434 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 28
11:38:49.464473 ARP, Request who-has 192.168.12.1 tell 192.168.12.15, length 46
11:38:49.464723 ARP, Reply 192.168.12.1 is-at 7c:5a:1c:9c:da:33 (oui Unknown), length 46
^C
65 packets captured
65 packets received by filter
0 packets dropped by kernel
EDIT 2:
Broadcom Gigabit Ethernet BCM5720
Intel(R) Gigabit 4P I350-t Adapter
root@LS-PVE-00:~# lspci -k | grep -A 3 -i ethernet
04:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720 Gigabit Ethernet PCIe
DeviceName: NIC1
Subsystem: Dell NetXtreme BCM5720 Gigabit Ethernet PCIe
Kernel driver in use: tg3
Kernel modules: tg3
04:00.1 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720 Gigabit Ethernet PCIe
DeviceName: NIC2
Subsystem: Dell NetXtreme BCM5720 Gigabit Ethernet PCIe
Kernel driver in use: tg3
Kernel modules: tg3
17:02.0 PCI bridge: Intel Corporation Sky Lake-E PCI Express Root Port C (rev 04)
pcilib: Error reading /sys/bus/pci/devices/0000:18:00.0/label: Operation not permitted
--
3b:00.0 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
3b:00.1 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
3b:00.2 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
3b:00.3 Ethernet controller: Intel Corporation I350 Gigabit Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter I350-T4
Kernel driver in use: igb
Kernel modules: igb
5d:05.0 System peripheral: Intel Corporation Sky Lake-E VT-d (rev 04)
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