Industrial Engineer · phase 5 of 16 · noun
MAC Address
Hardware-layer address assigned to an Ethernet network interface.
The Explain card
- Plain English
- The MAC address is the hardware identity burned into an Ethernet port at the factory. It is unique to the interface and has nothing to do with the IP address you assign.
- Example
- A device with no IP yet still announces its MAC address. The commissioning tool finds it by MAC, assigns an IP, and only then can the PLC reach it.
- Why it matters
- When a replacement module comes with a new MAC, anything that keyed on the old one, like a DHCP reservation or a switch port security rule, stops working. The MAC is also printed on the label, which makes it the fastest way to find a mystery device in a switch's table.
- Hook
- The serial number of the network port.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
During commissioning, the engineer reads the MAC Address from the managed switch table to verify that the replacement PLC is connected to port 7.
Why these words
- MAC English initialism of media access control specifies the networking layer associated with address
- Address Old French adrecier, to direct or make straight names the identifying label used by that layer
Where it came from
- Origin
- English networking phrase formed from the initialism MAC and the older noun address
- Entered the language
- 1980s
- What changed
- Address developed from the idea of directing something toward a place to naming locations and identifiers; MAC arose as shorthand for media access control.
How it is spelled
- Pattern
- MAC is written in capitals because it is an initialism.
- Pattern
- The two words are written separately.
- Pattern
- Address contains both double d and double s.
Spelled like
- IP address
- I/O address
- MAC table
Broken into chunks
-
MAC
- MAC table
- MAC filtering
- MAC layer
-
address
- IP address
- network address
- memory address
What it sits beside
Same subject
- Ethernet switch
- ARP table
- managed switch
- network interface
- DHCP reservation
Same shape
- IP address
- I/O address
- PLC address
network identifiers
- MAC Address
- IP address
- host name
switch diagnostics
- MAC address table
- port status
- VLAN membership
Where it sits in the deck
Phase 5: PLC Industrial Communications
The protocols that let controllers, drives and operator panels talk, plus the addressing and description files that make them agree on what was said.
