It's only migrating a VM with vlan tag 50, to this Proxmox node.
Migrating from:
task started by HA resource agent
2020-09-01 12:58:53 starting migration of VM 100 to node 'proxmox4' (10.0.0.14)
2020-09-01 12:58:53 starting VM 100 on remote node 'proxmox4'
2020-09-01 12:58:55 [proxmox4] Error: 8021q: VLAN device already exists.
2020-09-01 12:58:55 [proxmox4] can't add vlan tag 50 to interface bond0
2020-09-01 12:58:55 [proxmox4] kvm: network script /var/lib/qemu-server/pve-bridge failed with status 512
2020-09-01 12:58:55 [proxmox4] start failed: QEMU exited with code 1
2020-09-01 12:58:55 ERROR: online migrate failure - remote command failed with exit code 255
2020-09-01 12:58:55 aborting phase 2 - cleanup resources
2020-09-01 12:58:55 migrate_cancel
2020-09-01 12:58:56 ERROR: migration finished with problems (duration 00:00:03)
TASK ERROR: migration problems
Migrating to:
QEMU: Error: 8021q: VLAN device already exists.
QEMU: can't add vlan tag 50 to interface bond0
QEMU: kvm: network script /var/lib/qemu-server/pve-bridge failed with status 512
TASK ERROR: start failed: QEMU exited with code 1
Migrating from:
task started by HA resource agent
2020-09-01 12:58:53 starting migration of VM 100 to node 'proxmox4' (10.0.0.14)
2020-09-01 12:58:53 starting VM 100 on remote node 'proxmox4'
2020-09-01 12:58:55 [proxmox4] Error: 8021q: VLAN device already exists.
2020-09-01 12:58:55 [proxmox4] can't add vlan tag 50 to interface bond0
2020-09-01 12:58:55 [proxmox4] kvm: network script /var/lib/qemu-server/pve-bridge failed with status 512
2020-09-01 12:58:55 [proxmox4] start failed: QEMU exited with code 1
2020-09-01 12:58:55 ERROR: online migrate failure - remote command failed with exit code 255
2020-09-01 12:58:55 aborting phase 2 - cleanup resources
2020-09-01 12:58:55 migrate_cancel
2020-09-01 12:58:56 ERROR: migration finished with problems (duration 00:00:03)
TASK ERROR: migration problems
Migrating to:
QEMU: Error: 8021q: VLAN device already exists.
QEMU: can't add vlan tag 50 to interface bond0
QEMU: kvm: network script /var/lib/qemu-server/pve-bridge failed with status 512
TASK ERROR: start failed: QEMU exited with code 1