Zabbix item key is unsupported for some servers, but not for others

These network items appeared on "Zabbix Ubuntu" due to a Zabbix feature called low-level discovery.

If you go to "Discovery rules" on either of these hosts, you will see "Mounted filesystem discovery" and "Network interface discovery". Network items are created by the latter rule. This discovery rule runs once per hour by default, this might be one of the reasons you did not see network items on "Zabbix Centos" straight away. However, by the time this answer reaches you, you should probably already have them.

According to item documentation, vfs.file.cksum[] accepts a file name as the first parameter (unlike, for instance, logrt[] item), so a regular expression will not work there.

One possible approach would be to use a user macro here and define the item as follows:

vfs.file.cksum[/path/to/file/12{$VERSION}4_file.jar]

Then define the appropriate {$VERSION} macro for each host.

Alternatively, you can use low-level discovery to discover the files you want, but that would involve writing a UserParameter, which you would rather avoid. Meanwhile, there is a feature request for a built-in file discovery at ZBXNEXT-712 that you can vote on.