Setup IPv6 subnets on Linux
This is a guide on how to delegate a he.net IPv5 /48 subnet into multiple smaller networks that you can route and manage on your own network. This uses Linux as the base.
This is a necessary if you want to run IPv4 on another router that can't handle IPv6 for some reason, this adds a dedicated IPv6 router in parallel to the IPv4 router - dual stack.
Topology
/ ---- Router #2 ---- Hosts subnet #2
---- he.net ---- Router #1 ----
\ ---- Hosts subnet #1
Net info
(obfuscated to hide my ip range)
IP block: 2001:450:bb44::/48
Split into subnets
I decided to split the IP block into blocks of /117, 2048 addresses each, using http://www.gestioip.net/cgi-bin/subnet_calculator.cgi
The two networks I'm setting up now are:
Subnet #1: 2001:450:bb44::/117 - main subnet, router #1 needs to route subnet #2 to router #2 Subnet #2: 2001:450:bb44::800/117 - subnet connected to a router #2 which is behind subnet #1
Router for subnet #1
External (eth0) router IP: 2001:470:17:1e5::2/64 Default gateway: 2001:470:17:1e5::1/128 Internal (eth1) router IP: 2001:450:bb44::1/117
ip -6 route add 2001:470:17:1e5::2/64 via 2001:470:17:1e5::1 dev eth0
Add route 2001:450:bb44::801/117 via 2001:450:bb44::29 (this is another internal router)
ip -6 route add 2001:450:bb44::801/117 via 2001:450:bb44::29 dev eth1
Hosts behind subnet #1
Calculate or use https://www.ultratools.com/tools/ipv6CIDRToRange to convert the CIDR to the actual range.
Host IP: pick one between 2001:470:27:2d5::2 to 2001:470:27:2d5::7ff Netmask/block size: 117 Default gateway: 2001:450:bb44::1
Manually assign addresses to the hosts or use DHCPv6 to automate the process - radvd won't work since it requires /64 subnets.
Router for subnet #2
External (eth0) router IP: 2001:450:bb44::29/117 Default gateway: 2001:450:bb44::1/117 Internal (eth1) router IP: 2001:450:bb44::801/117
ip -6 route add 2001:450:bb44::29/117 via 2001:450:bb44::1 dev eth0
Enable IPv6 forwarding:
sysctl -w net.ipv6.conf.all.forwarding=1 and store it in /etc/sysctrl.conf
Hosts behind subnet #2
Host IP: pick one between 2001:470:27:2d5::802 to 2001:470:27:2d5::fff Netmask/block size: 117 Default gateway: 2001:450:bb44::801
Manually assign addresses to the hosts or use DHCPv6 to automate the process - radvd won't work since it requires /64 subnets.
Delete/remove subnets and host addresses
Find addresses/subnets:
route -n -6 ifconfig
Remove them:
ip -6 route del 2001:450:bb44::/64 dev eth0 ip -6 addr del 2001:450:bb44::1 dev eth0
Test connectivity
From subnet #2 ping router #1:
ping9 2001:450:bb44::1
Find IPv6 aaaa record from DNS:
dig google.com aaaa
