ISC DHCP 4.3.1
Today, a PowerDNS (open source dns, www.powerdns.com) deployment ran into
trouble with large amounts of IPv6 users. It appears a large telco 'flicked
the switch'. We had around 8000 DNS queries/s over IPv6, and everything
slowed to a crawl. 100% CPU utilization, most of it in the kernel. The same
amount of queries over IPv4 causes no problems.
Problem description: using DHCPv6 on SLC5 at CERN requires some tweaking of the network configuration files, due to a 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).
This page is obsolete and may no longer be relevant with the latest version of SLC6.
Problem description: an Ubuntu client doesn't configure the IPv6 address at boot time. But running manually "dhclient -6" works. dmesg reports:
[ 11.997321] type=1400 audit(1372427393.005:35): apparmor="DENIED" operation="open" parent=1053 profile="/sbin/dhclient" name="/var/lib/NetworkManager/dhclient6-eth0.conf" pid=1765 comm="dhclient" requested_mask="r" denied_mask="r" fsuid=0 ouid=0
- SLC5 may have the ipv6 module disabled. Please edit the file /etc/modprobe.conf and remove the lines disabling ipv6 (#alias ipv6 off, #options ipv6 disable=1); then reboot.
- SLC6 may have the ipv6 module disabled. Please edit the file /etc/modprobe.d/ipv6.conf and remove the lines disabling ipv6 (# options ipv6 disable=1); edit the file /etc/avahi/avahi-daemon.conf and set use-ipv6=yes; then reboot.
Add these lines to /etc/network/interfaces
iface eth0 inet6 static address 2001:1458:E008:0001::2 netmask 64 gateway 2001:1458:E008:0001::1 pre-up modprobe ipv6
Add these lines to /etc/sysconfig/network-scripts/ifcfg-eth0
Add these lines to /etc/sysconfig/network
WARNING: SLC5 images have the ipv6 module disabled. Please edit the file /etc/modprobe.conf and remove the lines which disable ipv6 (#alias ipv6 off, #options ipv6 disable=1); then reboot.
Problem description: a Linux client doesn't get the IPv6 client when it connects to the network
The client must send a DHCPv6 request with a DUID that contains the MAC address of the requesting interface. The MAC address must be registered in LANDB (Network database) in order to be allowed to get an address.