So, the SNMP Agent you're polling/querying (you didn't say which) is either hardcoded or configured not to provide this information. What does this mean for you? Well, the remote system must have a network interface otherwise you wouldn't be able to talk to it. And many of the RFC1213 packet/status counters in snmp were deliberately made obsolete when a 'safe' subset was adopted into RFC1907. I created an SNMP Agent recently and its support for 'standard' objects doesn't go anywhere near listing network interfaces. Why does anyone need access to know your system's MAC address? They probably don't. Nowadays, implementations tend to be far more conservative in the information they disclose, because every piece of information you disclose is potentially another way to attack your system. But next we have to consider that times have changed since the SNMP and SMI RFCs were written, well before the dot-com boom and back when the internet was a relatively pleasant and happy place. ifPhysAddress) is a column in a table of interfaces and you don't know in advance how many conceptual rows you'll get back (and what unique numerical index each row will use as its key).

Systems do not have MAC addresses network interfaces do, and a system may have zero, one, two or more network interfaces. There is no such thing as 'system MAC address'.

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