6RD and Debian/GNU Linux

Preface

The goal of this document is to explain how to configure Debian/GNU Linux router to obtain IPv6 6RD configuration details from the ISP DHCP server and to share IPv6 addresses from the obtained prefix to LAN hosts via Router Advertisement Daemon (radvd).

In short, this configuration enables IPv6 connectivity to the router itself and all connecting hosts.

This document assumes that eth0 is the external, internet facing network interface and eth1 is the internal, LAN facing one. You may need to adjust these depending on your configuration.

Configuration

Install the necessary packages
# sudo apt-get install radvd ipv6calc
Edit DHCP to request 6RD options

Edit /etc/dhcp/dhclient.conf and add the following:
option option-6rd code 212 = { integer 8, integer 8, integer 16, integer 16, integer 16, integer 16, integer 16, integer 16, integer 16, integer 16, array of ip-address }; Also adjust the 'request' line to include the 'option-6rd' just added:
request subnet-mask, broadcast-address, time-offset, routers, interface-mtu, rfc3442-classless-static-routes, option-6rd;
Add 6RD configuration script

Create /etc/dhcp/dhclient-exit-hooks.d/option-6rd script with the following (while adjusting LANIF to your LAN interface!) content:
#!/bin/bash # # 6RD DHCP configuration script # # Based on many existing scripts, such as: # 1) dhclient-6rd by Nathan Lutchansky for Ubuntu 10.04 # 2) Alexandre Beloin http://beloin.net/doc/6rd.txt # # This script is public domain. # # # ************************* Installation Instructions ************************* # # 1) Place this script in /etc/dhcp3/dhclient-exit-hooks.d/option-6rd to assign IPv6 adresses # 2) Script asumes eth1 - ISP link, eth0 - LAN link # 3) Do not forget to turn on ipv6 forwarding # 4) apt-get install ipv6calc # 5) You must edit /etc/dhcp3/dhclient.conf to add the option-6rd definition: # # option option-6rd code 212 = { integer 8, integer 8, integer 16, integer 16, # integer 16, integer 16, integer 16, integer 16, # integer 16, integer 16, array of ip-address }; # # 6) In the same file you must also add option-6rd to the "request" list !!!!!!!!! # 7) apt-get install radvd # # ***************************************************************************** # PATH=/sbin:/usr/local/bin:$PATH log_6rd() { ##$new_ip_address, and the interface name is passed in $interface WANIF=$interface LANIF="eth1" WANIP4=$new_ip_address if [ -z "$new_option_6rd" ]; then logger -p daemon.info -t option-6rd "no 6RD parameters available" return fi OPTFILE="/run/dhcp-option-6rd.${WANIF}" if [ -e "${OPTFILE}" ]; then old_option_6rd="`cat ${OPTFILE}`" else old_option_6rd="" fi if [ "${new_option_6rd}:${WANIP4}" == "${old_option_6rd}" ]; then logger -p daemon.info -t option-6rd "no 6RD parameter change" return fi echo "${new_option_6rd}:${WANIP4}" > ${OPTFILE} srd_vals=(${new_option_6rd}) srd_masklen=${srd_vals[0]} srd_prefixlen=${srd_vals[1]} srd_prefix="`printf "%x:%x:%x:%x:%x:%x:%x:%x" ${srd_vals[@]:2:8} | sed -E s/$:0$+$/::/`" srd_braddr=${srd_vals[10]} ipsep=(${new_ip_address//\./ }) if (( srd_masklen==0 )); then srd_relayprefix=0.0.0.0 elif (( srd_masklen <= 8 )); then masked=$((${ipsep[0]} & ~((1 << (8 - srd_masklen)) - 1))) srd_relayprefix=${masked}.0.0.0 elif (( srd_masklen <= 16 )); then masked=$((${ipsep[1]} & ~((1 << (16 - srd_masklen)) - 1))) srd_relayprefix=${ipsep[0]}.${masked}.0.0 elif (( srd_masklen <= 24 )); then masked=$((${ipsep[2]} & ~((1 << (24 - srd_masklen)) - 1))) srd_relayprefix=${ipsep[0]}.${ipsep[1]}.${masked}.0 elif (( srd_masklen <= 32 )); then masked=$((${ipsep[3]} & ~((1 << (32 - srd_masklen)) - 1))) srd_relayprefix=${ipsep[0]}.${ipsep[1]}.${ipsep[2]}.${masked} else logger -p daemon.info -t option-6rd "invalid IPv4MaskLen $srd_masklen" return fi logger -p daemon.info -t option-6rd "6RD parameters: 6rd-prefix ${srd_prefix}/${srd_prefixlen} 6rd-relay_prefix ${srd_relayprefix}/${srd_masklen} br ${srd_braddr}" delagated_prefix=`ipv6calc -q --action 6rd_local_prefix --6rd_prefix ${srd_prefix}/${srd_prefixlen} --6rd_relay_prefix ${srd_relayprefix}/${srd_masklen} $WANIP4` ifname_ip6addr="$(echo "$delagated_prefix" | awk '{split($0,a,"/"); print a[1]}')1/$(echo "$delagated_prefix" | awk '{split($0,a,"/"); print a[2]}')" lan_ip6addr="$(echo "$delagated_prefix" | awk '{split($0,a,"/"); print a[1]}')1/64" # Need to change if using subnet (if Delagated prefix < 64) lan_ip6net="$(echo "$delagated_prefix" | awk '{split($0,a,"/"); print a[1]}')/64" # Need to change if using subnet (if Delagated prefix < 64) # stop radvd, remove old tunnel & global ipv6 addresses /etc/init.d/radvd stop ip tunnel del 6rdif 2>/dev/null ip -l 5 -6 addr flush scope global dev $LANIF ip tunnel add 6rdif mode sit local $WANIP4 ip tunnel 6rd dev 6rdif 6rd-prefix ${srd_prefix}/${srd_prefixlen} 6rd-relay_prefix ${srd_relayprefix}/${srd_masklen} ip link set dev 6rdif up ip -6 addr add "$ifname_ip6addr" dev 6rdif ip -6 route replace default via ::${srd_braddr} dev 6rdif metric 1 ip -6 addr add $lan_ip6addr dev $LANIF # Enable routing back to LAN interface ip -6 route replace "$delagated_prefix" dev $LANIF metric 1 echo " interface $LANIF { AdvSendAdvert on; MinRtrAdvInterval 3; MaxRtrAdvInterval 10; AdvLinkMTU 1280; prefix $lan_ip6net { AdvOnLink on; AdvAutonomous on; AdvRouterAddr on; AdvValidLifetime 86400; AdvPreferredLifetime 86400; }; }; " > /etc/radvd.conf /etc/init.d/radvd start # NOTE: optionally reload IPv6 firewall script here } case $reason in BOUND|RENEW|REBIND|REBOOT) log_6rd ;; esac
Edit /etc/sysctl.conf and make sure IPv6 forwarding is enabled:
net.ipv6.conf.default.forwarding=1
Take the external network interface down and up again to enable the new configuration

For example:
# sudo ifdown eth0 # sudo ifup eth0