How to find out the original MAC address from a network adapter with manually modified MAC address:

root@core:~# ethtool -P eth3
Permanent address: 10:a2:bc:86:22:16

How to disable ipv6 for a specific network adapter:

root@core:~# echo 1 > /proc/sys/net/ipv6/conf/iscsi/disable_ipv6

How to manually change the network adapter MAC address:

root@core:~# ifconfig eth3 | grep HWaddr
eth3      Link encap:Ethernet  HWaddr c3:de:c3:65:g3:4t
root@core:~# [color=green]ifconfig eth3 hw ether 10:a2:bc:86:22:16[/color]
root@core:~# ifconfig eth3 | grep HWaddr
eth3      Link encap:Ethernet  HWaddr 10:a2:bc:86:22:16