But what about multi-homed hosts that have multiple interfaces exposed to Zabbix network discovery?

1. Let's return to Configuration | Discovery and click on A test discovery.
2. Look at the Device uniqueness criteria option—the only setting there is IP address. In the Checks block, click on New and choose Zabbix agent in the Check type drop-down. In the Key field, enter system.uname, and then click on Add in the Checks block.
3. Notice how the Device uniqueness criteria got a new option—Zabbix agent "system.uname", as shown in the following screenshot:

By default, with the uniqueness criteria set to IP address, Zabbix will create a new host for each discovered IP address. If there's a system with multiple addresses, a new host will be created for each address. If the uniqueness criteria is set to a Zabbix agent item, it will look at all the IP addresses it has seen before and the values it got back for that item key. If the new value matches some previous value, it will add a new interface to the existing host instead of creating a new host. It works the same way with SNMP—adding an SNMP check will add another uniqueness criteria option, and Zabbix will compare values received for that specific OID. It is common to discover SNMP devices by the SNMPv2-MIB::sysDescr.0 OID.

Now that we have discussed network discovery, I'll give you one short suggestion about it—don't use it. Well, maybe not that harsh, but do not cling to it too much. There are use cases for network discovery, but quite often, there's a decent list of devices that should be monitored coming either from a configuration management database (CMDB) or some other source. In that case, it is better to integrate and automatically update your Zabbix configuration based on that authoritative source. If your answer to What's your most definitive list of hosts in your environment? is Zabbix, then network discovery is for you.