Calculate 6RD prefixes from DHCP (IPv4) OPTION_6RD (212).

Either use this library or the included 6rdcalc command.

This tool is useful for scripting, e.g. when used in a dhclient hook.

There's ipv6calc, why create a new tool? This tool is written in Go, so it's easily portable to multiple architectures. Since it also does OPTION_6RD parsing, it saves you from calculating the initial prefix in sh/ash/Bash and lets you easily create new /64 prefixes for your networks (LAN, device, docker, etc.).

go install github.com/mafredri/ipv6rd/cmd/6rdcalc@latest

Other platforms:

git clone https://github.com/mafredri/ipv6rd.git
cd ipv6rd
GOOS=linux GOARCH=mips go build ./cmd/6rdcalc
scp 6rdcalc unifi-security-gateway.local:
ssh [email protected]
ubnt@unifi-security-gateway:~$ ./6rdcalc

Generating the tunnel configuration from the given 6RD configuration:

6rdcalc tunnel 84.240.100.100 "14 38 8193 8195 62464 0 0 0 0 0 84.251.255.254"

The value for IP comes from $new_ip_address and the value for OPTION 6RD comes from $new_option_6rd, both available in a dhclient hook.

Example output:

PREFIX="2001:2003:f400::/38"
RELAY_PREFIX="84.240.0.0/14"
BORDER_RELAY="::84.251.255.254"
DELEGATED_PREFIX="2001:2003:f464:6400::/56"
TUNNEL_ADDRESS="2001:2003:f464:6400::/128"

Usage in scripts:

eval "$(6rdcalc tunnel 84.240.100.100 "14 38 8193 8195 62464 0 0 0 0 0 84.251.255.254")"
echo "$DELEGATED_PREFIX"

Use the network subcommand to slice a /64 out of your delegated prefix.

6rdcalc network 2001:2003:f464:6400::/56 0:0:0:10::1/64

The DELEGATED PREFIX comes from the tunnel configuration and the IP is the wanted network IP in CIDR notation, without the delegated prefix.

Example output:

NETWORK="2001:2003:f464:6410::/64"
ADDRESS="2001:2003:f464:6410::1/64"
IP="2001:2003:f464:6410::1"

Usage in scripts:

eval "$(6rdcalc network 2001:2003:f464:6400::/56 0:0:0:10::1/64)"
echo "$IP"

Use the contains subcommand to figure out if your existing configuration needs updating.

DELEGATED_PREFIX="2001:2003:f464:6400::/56"
ADDRESS="2001:2003:f464:6410::1/64"
IP="2001:2003:f464:6410::1"

$ 6rdcalc contains "$DELEGATED_PREFIX" "$IP"
true
$ 6rdcalc contains "$DELEGATED_PREFIX" "$ADDRESS"
true
6rdcalc contains "$DELEGATED_PREFIX" "2001:2003:f464:0000::1"
false

option option-6rd code 212 = { integer 8, integer 8, ip6-address, array of ip-address };
# OR
option option-6rd code 212 = {
	integer 8, integer 8,
	unsigned integer 16, unsigned integer 16, unsigned integer 16, unsigned integer 16,
	unsigned integer 16, unsigned integer 16, unsigned integer 16, unsigned integer 16,
	array of ip-address
};

interface "eth0" {
	also request option-6rd;
}

• RFC5969 - IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)
• bonan/dhcp6rd