SUMMARY (2) More thorough summary on Changing MAC Address

From: Sean Carnes (
Date: Mon Aug 10 1998 - 23:50:27 CDT

For those who dont know I am posting a more thorough summary of the MAC
address problem.

Sun Machines come with a MAC address on the motherboard.   If you have two
ethernet interfaces they are both give the same MAC address.  This can cause
problems if they are both hooked up to the SAME hub and the same network
segment.  This is usually not the case but in my case it could not be
avoided.  I needed to stop the duplicate packets from hitting both
interfaces so I needed to change the MAC address of one of the interfaces. 
There are other ways, I KNOW, but this was the only solution.  I change the
interface by putting this command in the /etc/init.d/inetsvc script:

ifconfig hme0 ether xx:xx:xx:xx:xx:xx
ifconfig hme1 ether xx:xx:xx:xx:xx:xx

This fixed the problem. 

Some interesting thigs to note are:

1)  Only the Sun Quad cards come with MAC addresses in them.  THe other Sun
ethernet cards just use the motherboards, unless changed.
2)  If you change the MAC address there is some SMALL chance that there may
be another with the same address.  I just added one to the last hex but some
people have come up with corporation wide solutions.  Mine is easy though,
add one and you have another interface.  If any problems result from this I
say tough to everyone else I made it so it is mine.
2)  Solaris 2.6 has an option that you can set in ndd call 
ip_enable_group_ifs which should so load balancing between the interfaces. 
I cant find any good information on this though.  If anyone has some good
information let me know.
3)  Solaris 2.6 ifconfig does not let you see the MAC address unless you are
3)   Use switches I hate HUBS!!!  ;)

I probably left something out so ask me.  I now know everything about MAC
addresses but I have to go home.

Sean Carnes
Systems Administrator

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