Can someone explain to me why, if MAC address is an address, "...issued at the factory and do not change.", how a device can have more than one MAC address?
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How Can A Device Have More Than One MAC Address?
JH
John Honovich
Mar 23, 2015Frank, one example: your computer has multiple NICs, e.g., you have a 100Mb/s Ethernet wired connection and a WiFi connection. Each would have its own MAC.
There are many other combinations like a server having multiple wired Ethernet connections or a laptop having WiFI and 4G connections, etc.
FT
Frank Tees
Mar 23, 2015I should have been more specific. How can a camera have more than one MAC address?
JH
John Honovich
Mar 23, 2015Which cameras have more than one MAC address?
A camera with wireless and wired output would, but besides that, which specific cameras have you seen with multiple MAC addresses?
FT
Frank Tees
Mar 23, 2015I haven't. My question is really about Question 6 on Quiz #2. Perhaps a discussion about this should be postponed until after the end date for the quiz.....
Brian Rhodes
Mar 23, 2015Hello Frank:
The MAC is associated with the NIC, not the device. If a device has multiple NICs (ie: Wired/WiFi interfaces, like John H mentions), two MACs are possible.
When a camera has only one NIC (like the majority do), we can use the MAC as a unique identifier for a camera. However, this is not always a guarantee, and this question enforces that point.
Does that help?
Brian Rhodes
Mar 23, 2015Thanks for bringing this point up. I revised & added a section to the Network Addressing for Video Surveillance Guide reading make this clear:
"Multiple MACs Possible but UnlikelyIf a device has multiple network interfaces, it may have more than one single MAC address. The MAC is associated with a device's network interfaces, but not the general device. In the case of cameras with multiple network connections, like a camera with both a wired ethernet port and an integrated wireless radio, the device could have more than a single MAC address.
However, since the vast majority of cameras include only a single ethernet port, the MAC address may indirectly be used to describe the entire camera."
Ethan Ace
Mar 23, 2015Another example: The Sony SNT four-channel encoders have four MAC addresses, four IP addresses, but only one Ethernet port.
UI
Undisclosed Integrator #1
Mar 23, 2015Dedicated micros seem to use dual Mac addressing...
Brian Rhodes
Mar 23, 2015I believe the DM 'IPTV' system authenticates devices by both MAC and VLAN per an access list. (This is the 'dual part'.) As such, it is a matter of network authentication (ie: Network Security) rather than pure addressing.
The entire DM IPTV approach is a little odd and a rather extreme solution (using proprietary switches) to a problem more easily and conventionally dealt with using standard access lists and port security in managed switches.
FYI: We will discuss Network Security (both simple and extreme methods like 802.1x for IP Cameras) in the Thursday class of Week #4.
VL
Vincent Loustau
Mar 24, 2015Hi,
If you have a device that has 2 different kinds of network connection (for example 2 ethernet ports, or 1 ethernet port + WiFi), you will have 2 different mac adress.
It's because you have 2 different hw boards that manage each network connection, and each board has it's own mac adress.
John Ringis
Mar 26, 2015I am currently testing a new NVR and it has two seperate ethernet connections. The MAC address on each port is different. In this case, I have two seperate devices in the same chassis that manage seperate network connection...and each port/device has it's own MAC adress.
EM
Efrain Morales
Mar 27, 2015which nvr have more than one mac address?
UI
Undisclosed Integrator #1
Mar 27, 2015Seen a few, take the Hikvision range they have two NICs so two MAC addresses :)
JH
John Honovich
Mar 27, 2015Any NVR with multiple NICs will have multiple MAC addresses. This is increasingly common for mid to high end NVRs.
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