MAC address

[Marco_163]

Is it possible to change MAC address on Ethernet card?

[Fred Ruffet]

No. MAC address identifies a network equipement and should not be changed.

Regards,

Fred

[Michael_356]

lanadmin -A 0x will do so
Have a look an man lanadmin

Michael

[T G Manikandan]

MAc addresses are unique and fixed during manufacture.

to my knowledge you cannot!

[Sridhar Bhaskarla]

Hi,

Yes but it is not something I would like to do.

Run the command

lanadmin -A mac_address

lanadmin -A 0x0011183F876AB 2

will set the above MAC for lan2 card.

man lanadmin for more info. However, it will not survive the reboots. You will need to edit /etc/rc.config.d/hpconf file and add the mac address there. is tyep of the lancard. For BT lancards, it would be hpbtlanconf.

HP_BTLAN_INTERFACE_NAME[0]=lan2
HP_BTLAN_STATION_ADDRESS[0]=0x0011183F876AB
HP_BTLAN_SPEED[0]=100FD

You don't need to specify need if you set it to auto negotiation.

Note that you cannot use lanadmin on all the interfaces.

-Sri

[G. Vrijhoeven]

Hi,

It is possible, just be sure you know what you are doing...

in /etc/rc.config.d/ you have several lan config files. In those files you are able to set speed/duplex settings and Station address of interfac.
e.g.:

hpbtlanconf
hpbase100conf
etc.

HTH,

Gideon

[Slawomir Gora]

Hi,

yes you can do it. If you want set it permanently go to file:
/etc/rc.config.d/hppci100conf for btlat5 card

or read manual to lanadmin command.

[Muthukumar_5 · Accepted solution]

we can do it with lanadmin / lanconfig files.

Collect the station address as,

lanscan -s

IF you are going to change 2nd interface then,

lanadmin -a 1 or lanscan
-- > MAC address for lan1


You can change it with sam as,

sam --> network and communications --> network interface cards --> select interface and actions-modify --> advanced options --> specify the hardware address

Regards
Muthu

[Steve Lewis]

Sometimes you have to. I have been to one installation which had switch ports somehow 'locked' to one particular MAC address with auto-lock-out when any other interface was connected.
As part of their on-site contingency procedures, they had to manually unplug the primary server and plug in the standby, which caused big problems. The solution was to change the MAC address of the standby server when it was plugged in. A better solution would have been to keep both machines plugged in permanently.

Note that some earlier cards, such as the built-in interfaces to D and K class servers don't allow you to change it.

[Sยภเl Kย๓คг]

See the MAC Address is unique for LAN cards which is given by the manufaturer at the time of manufaturing .This address is burned in to the LAN Card and cannot modify it by hardware.But if required u can modify it in the OS to accomapny the change as explained by our Gurus above
regards
SK

[László Zsolt]

Under windows Xp Prof you can change your Ethernet card MAC adress.

Go to the LAN connection, and right click on it, then choose Properties. In the next window you want to Configure your Ethernet Card. After that choose Advanced and Local Administrated Address. In Value field you can give it the new MAC address.

[Marco_163]

I noticed that I losted network connections on all network interfaces after changed MAC address on one of them.
I change the MAC adress by SAM tool.
Is it possible to lost network connection only on interface that I change MAC address?

[Muthukumar_5]

Did you change the hardward address of only one?? What is the status now!? Is it working or not? check with linkloop command.

linkloop -i

Before changing the station address try as,

1. Bring down the lan
2. Change the Mac Address
3. Bring up the lan...

It is good to do as temporary one as,

1. ifconfig down lan

Note: Try to check on testing interface

2. lanadmin -A 0x

3. ifconfig up lan

See the lanadmin page for -A option as,

-A station_addr Set the new station address of the interface
corresponding to PPA. The station_addr must
be entered in hex format with a '0x' prefix.
You must have superuser privileges. When
station_addr is DEFAULT, the factory default
physical address will be restored.

WARNING: To ensure the interface and the
system work correctly, the interface MUST be
brought down before setting the new station
address. After the new station address is
set, the interface should be brought up in
order to be functional. See ifconfig(1M) for
bringing down and bringing up the interface.

-Muthu

[Bill Hassell]

Yes, you will lose network connections when you change the MAC address. The reason most computers using TCP/IP will have a local ARP cache of MAC addresses and the hostname associated with that MAC address. Type the command:

arp -a

on a working computer and you'll see the current ARP cache. You can use arp -d to remove the entry and then try to connect to the changed computer. Eventually, the arp cache will drop entries that have not been recently used and you can start connecting. This could take a long time. Rebooting all your computers will fix the problem. (as you can see, changing the MAC address is not recommended with the exception of HP's MC ServiceGuard)

[rick jones]

Changing the MAC address of an interface could conceiveably cause the loss of TCP connections if the remote systems (or the interving router) does not refresh their ARP entries sooner than their TCP gives-up on a connection. In HP-UX 11.X terms, if one of the entries in ndd -h | grep arp (I cannot remember which right now) is longer than tcp_ip_abort_interval.

Why? Because all those systems will be using the OLD MAC address, but the NIC will not take-in frames to that OLD address when you change it to the new address.

I've heard that some Cisco kit is rather, well, slow, to update its ARP tables.

[bob smith_38]

The MAC address is burned into the chip at manufacture time. Each manufacturer uses a specified range of mac addresses, so you could conceivably identify the manufacturer via the first part of the mac address.

It IS changeable, in the chip itself! This is accomplished via a EEPROM chip (Electronically Eraseable, Programmable Read-Only Module). These chips followed the EPROM (just eraseable) which used a special infrared lamp to erase the chip (these still occur on systems-look for a chip with a round sticker in the middle of it, there's a lense underneath).

MAC addresses are changed all the time in network land. In theory, there should eb NO duplicatioin of a mac address in a manufacturer's line, but process isn't perfect...

So...we can change mac addresses (this is more heavily used in Netware, where the mac address is more directly controlled by admins, and has more impact on the IPX protocol, routing, performance, etc.)

Each brand/model of NIC has a downloadable tool which runs on a dos boot floppy to change the MAC address, OR it supports change within NT (or later).

Good luck!