SUMMARY: Multihoming my Ultra 10

From: Austin, Annie (
Date: Mon Jul 03 2000 - 10:46:29 CDT

The MAC address of a Sun host is by default that of the backplane on the box
as opposes to that of the NIC. To have the host use the individual MAC
addresses you can set a nvram parameter:


Only do this if you have both NICs on the same subnet. If like me, you will
have them on separate networks (like for a firewall) then leave the MAC
address settings alone.

You can also set this from withing UNIX using the ifconfig command:

Quite from Jarrett Carver []

"'ifconfig le1 ether aa:1:2:3:4:5' This sets the ethernet for an interface.
You will need to set both, although you can use the systems MAC address, it
will need to be set manually."

One other important point was made by Terry Gardner

"> Why is this done? How would I alter the MAC address? Which MAC address of
> the 2 should be altered?

Don't alter either unless you use Sun Cluster."

I have appeneded all replies so far to the bottom of this mail. I was also
reminded that the archives for this list have many good points to make on
this (and many other) issues.

Thanks to all who replied;

Chad Hodges
Jarrett Carver
Terry Gardner
Reichert, Alan
Hans Schaechl
David Evans

--- Replies in full ---

As long as they are on seperate networks there is no reason to change the
The ethernet spec says 'each workstation should have it's own unique MAC'
implies that there should not be multiple MACs. There is a boot-prom
that will allow you to make each MAC unique and there is also an ifconfig,
but I
never use either.


Check out the archives for this group. There was an excellent summary
done some months back on this. And check out as all the
steps are in there too but its not titled the way you would expect (and
I've lost the link I had for it).



The easiest way to make sure each NIC has its own MAC address is to set the use-local-mac? parameter to true at the OBP. (I could be wrong about the

name, but a printenv will show you everything, and that's relatively close).

I've seen this cause problems in jumpstart environments, though, because the initial RARP request uses the MAC in the OBP, and later requests use the MAC of the card. If you're not jumpstarting, though, don't worry about it.

Hope this helps, Chad Hodges


the MAC address. However, if both interfaces are on the same network you will have to change the MAC address.

This is done due to the fact that when packets are sent the IP address is actually translated to the MAC address. You can read up on this in many networking articles.

To do this you will need to:

'eeprom local-mac-address? true' By setting this to you are telling your system not to use the default system MAC address which is in your nvram. BY default this is set to false, hence all interfaces are set to the ethernet address that is programmed in the nvram. This is done by sun and will ensure

that all ethernet address are different.

'ifconfig le1 ether aa:1:2:3:4:5' This sets the ethernet for an interface. You will need to set both, although you can use the systems MAC address, ti will need to be set manually.

Now to have this re-occure accross reboots you will need to edit your RC scripts so that when the cards are configured they also configure these ethernet addresses.

Hope this is clear, I am hopped up on MT. Dew right now and am not sure how clear I am coming accross ;-)

Check you man pages on ifconfig and eeprom. ---

> I need to add an additional NIC into my Ultra 10. I have seen other Sun > servers multihomed and the MAC address of the cards are the same.

Correct. The MAC address on a Sun box comes from the backplane or centerplane, not the NIC card.

> > > Why is this done? How would I alter the MAC address? Which MAC address of > the 2 should be altered?

Don't alter either unless you use Sun Cluster.


This happens because one of the PROM settings is set to use the local MAC address of the machine (usually the MAC address of the on-board interface port).

You will need to get into the PROM settings and set the parameter to use the local MAC address to FALSE. Once this is done, and the machine is rebooted, then each interface will use it's own local MAC address.

- Alan --- Hi Annie,

generally SUNs MAC addresses are machine-based, not NIC- based. This results with all NICs on a machine having the same MAC address. If your NIC is of newer type (hme, qfe, ge etc.) and supports individual MAC per interface, you can enable NIC based MACs by setting the NVRAM parameter

local-mac-address?=false to local-mac-address?=true

Having the same MACs on more than one interface is ok as long as the NICs don't share the same physical ethernet subnet. Please be aware that older interface cars like the lance ethernet interfaces le-type don't support indi- vidual MACs, they'll all share the systems MAC address, ignoring the NVRAM setting.

You can also change the MAC of a NIC by ifconfig but you shouldn't need to.

Hth, Hans


leet ;-)

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