This page is obsolete and may no longer be relevant with the latest version of SLC6.

Problem description: using DHCPv6 with old version of SLC6 at CERN requires some tweaking of the network configuration files, due to s RedHat bug (https://bugzilla.redhat.com/show_bug.cgi?id=591630, https://bugzilla.redhat.com/show_bug.cgi?id=634857) and the way devices are authorized to connect to the network at CERN (i.e. by MAC address identification). The bug has been fixed in July 2014.

Solution: Follow these steps:

1) Allow DHCPv6 replies in ip6tables.

In /etc/sysconfig/ip6table add this line (before the REJECTs):

-A INPUT -m state --state NEW -m udp -p udp --dport 546 --sport 547 -s fe80::/10 -d fe80::/10 -j ACCEPT

2) Set the correct MAC address in the DUID.

If the device as multiple interfaces, create the file /etc/dhcp/dhclient.conf and declare the mac address of the ethernet interface registered in the IT-CS network database:

interface "eth0" {
    hardware ethernet 00:15:5D:FF:4A:DD;
}

In alternative, register all the mac addresses defined into the IT-CS network database (MAC addresses are shown by the ifconfig command)

3) Enable DHCPv6 at boot time

In the file  /etc/sysconfig/network-scripts/ifcfg-eth0 add the line
 DHCPV6C=yes

4) Delete the file /var/lib/dhclient/dhclient6.leases which may contain a wrong identifier (DUID) used on another attempt.

5) Restart the network service, or reboot the server