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Using the WIDE DHCPv6 Client on Online.net dedicated servers
Initially published on 2014-08-29
Pre-requisites
Debian-only.
Check the file /etc/modprobe.d/local.conf
, it may contain a line like this one:
options ipv6 disable=1
Since the default Debian kernel has IPv6 built-in rather than as a module, that line will not take effect. However it's better to remove or comment it out anyway, in case you install a different kernel later.
Installing WIDE DHCPv6
- setup-dhcpv6.sh
#!/bin/bash DUID=$1 IFACE=$2 if [ "$DUID" == "" ]||[ "$IFACE" == "" ]; then echo "Please specify your DUID and network interface!" exit 1 fi apt-get install -y wide-dhcpv6-client vim-common /etc/init.d/wide-dhcpv6-client stop echo 'profile default { script "/etc/wide-dhcpv6/dhcp6c-script"; };' > /etc/wide-dhcpv6/dhcp6c.conf echo "id-assoc pd { prefix-interface $IFACE { }; };" >> /etc/wide-dhcpv6/dhcp6c.conf echo "id-assoc na { };" >> /etc/wide-dhcpv6/dhcp6c.conf echo "interface $IFACE { send ia-na 0; send ia-pd 0; };" >> /etc/wide-dhcpv6/dhcp6c.conf echo $DUID | awk '{ gsub(":"," "); printf "0: 0a 00 %s\n", $0 }' | xxd -r > /var/lib/dhcpv6/dhcp6c_duid /etc/init.d/wide-dhcpv6-client start
Download and run this with the online.net DUID for the subnet you want to use specified, and the uplink interface name, for example:
wget -O setup-dhcpv6.sh https://version6.ru/_export/code/en/online.net-wide-dhcpv6?codeblock=1 chmod +x setup-dhcpv6.sh ./setup-dhcpv6.sh 00:03:00:01:23:45:67:89:ab:cd eth0
When the WIDE setup screen appears and asks on which interfaces to listen for DHCPv6, leave that at its default value and just press Enter.
Startup failure
Sometimes, for whatever reason, after running the above script, the DHCPv6 client fails to start. Just try:
/etc/init.d/wide-dhcpv6-client restart
…and this time it should start up properly.
Prevent outgoing request flood
Very rarely (happened just once yet, in months), WIDE can fail in a mysterious way and start sending SOLICIT requests continuously, without any back-off time in between. This can be detected by upstream as malicious flood and make them unhappy.
To prevent this issue, add the following into your ip6tables configuration:
ip6tables -A OUTPUT -p udp --dport 547 -m limit --limit 10/min --limit-burst 5 -j ACCEPT ip6tables -A OUTPUT -p udp --dport 547 -j DROP
…or just add this into /etc/rc.local
if you don't use any other ip6tables rules.
Other HOWTOs
- Online.net IPv6 prefix discovery using KAME-dhcp6c on FreeBSD (thanks for the awk+xxd line)