Zabbix proxy group error when upgrade from 7.4.3 to 7.4.5

[jvilafe]

I'm seeing errors in all my Zabbix proxies after updating the server and proxies to 7.4.5.

All the proxies are showing host assignment errors:

"Cannot send list of active checks to 'xxx.xxx.xxx.xxx'": host 'blablabla' is monitored by another proxy."

However, the hosts are correctly assigned to the proxy group member in the Zabbix server. The proxy member showing the error does NOT have the host assigned.

The error persists even after restarting the Zabbix proxy services.

Everything worked perfectly with 7.4.3.

[Andrejs Poddubņaks]

Hi!
The problem you described may be related to the agent requesting active checks from the wrong proxy.
At any given moment, a host that is “monitored by a proxy group” is actually assigned to one specific proxy within the group. If an agent sends an active check request to another proxy, it responds with “host is monitored by another proxy” and writes this error to the log.
After updating to 7.4.5, the host -> proxy assignment may have changed slightly, so now you see such messages on a larger number of proxies.

Possible solution:
1. Open the problematic host in Data collection -> Hosts.
2. Ensure that the proxy group is selected in the Monitored by field, rather than an individual proxy.

For proxy groups, Zabbix recommends the following in zabbix_agentd.conf / agent2.conf:
For passive checks: Server=proxy1,proxy2
For active checks = ServerActive=proxy1,proxy2

You need to make sure that:
There are no old/deleted proxies;
The agent does not knock on a proxy that no longer “owns” this host.

The problem is usually not with version 7.4.5 itself, but with the fact that agents access multiple proxies, while the host is bound to only one. Once the Server / ServerActive settings on the agents are brought into line with the proxy group configuration, the errors will disappear.

I hope It will help you!

[jvilafe]

Hello,

Yes, that's the problem. After migrating to 7.4.5 from 7.4.3, many hosts are actively trying to report to the proxy group they're not assigned to. For example, the host appears in the Zabbix Server as assigned to proxy-group01, which has 3 members. The system assigns proxy number 2 to the host, but the host's agent2 tries to report to proxy number 1 in the group.
Refreshing the configurations of proxy numbers 2 and 1, and agent2, doesn't resolve the issue. Restarting the proxies and agent2 doesn't either. This has happened with ALL proxy groups after the update, and it didn't occur with 7.4.3.

The only way I've been able to "fix" it is by creating new native 7.4.5 proxies from scratch on new VMs (Debian 13.2 + MySQL + Zabbixproxy) with the same IPs as the old ones, new proxy groups, and reassigning all the hosts from the old proxy groups. Restarting agent2 then works, but something goes wrong during the migration process from 7.4.3 to 7.4.5.