https://en.wikipedia.org/wiki/Unique_local_address
https://www.rfc-editor.org/rfc/rfc4193#section-3.2.2
http://www.sixxs.net/tools/grh/ula/list/
I have been looking for a local script to generate ULAs; there are many online generators (and a few bad/broken) ones; I wanted a local script.
There already exists this github repository with a bash script that generates ULA. It is written to run interactively and asks for mac address (and confirm an ntp query).
This should be run on a physical machine; not on an emulated system or virtual env. Tune the if variable according to needs.
if=eth0
t="$(ntptime | grep "time " | head -n1 | awk '{print $2}')"
EUI_48="$(ip a s dev $if | grep "link/ether" | awk '{print $2}')"
EUI_64="$(ipv6calc --action prefixmac2ipv6 --in prefix+mac --out ipv6addr :: $EUI_48 | sed 's/^:://')"
conq="$(echo "$t $EUI_64" | tr -d ".: ")"
sha1="$(for x in $(echo "$conq" | sed 's/\(..\)/\1 /g') ; do printf "\x${x}" ; done | sha1sum | awk '{print $1}' | tail -c 11 | sed 's/\(..\)/\1 /g')"
ULA="$(echo $sha1 | awk '{print "fd" $1 ":" $2 $3 ":" $4 $5 "::/48"}')"
echo "$t $EUI_48 $EUI_64 $conq=> $ULA"
By the way, ipv6calc is designed to produce the link local address this way:
ipv6calc --action prefixmac2ipv6 --in prefix+mac --out ipv6addr fe80:: $EUI_48
If you don't want to install ipv6calc, here is a function to convert EUI-48 into EUI-64: https://gist.github.com/mej/592da948323fc58455c1
You can easily generate valid ULAs in bash by only using the builtin printf and the special Bash variable $RANDOM:
printf "fd%x:%x:%x:%x::/64\n" "$(( $RANDOM/256 ))" "$RANDOM" "$RANDOM" "$RANDOM"
Running this several times on my own machine give me a bunch of freshly-minted (and more importantly, valid) ULA addresses with random subnet ids:
fd45:364c:99:6690::/64
fd19:59c8:7e73:30d7::/64
fd0c:4ebe:60ce:7a02::/64
...
If you want to only use one ULA network and multiple subnet ids per site, leave out the last two bytes and assign the subnet id manually as required:
fd45:364c:99::/64
fd45:364c:99:1::/64
fd45:364c:99:2::/64
Before you use a ULA, make sure to run the command a couple of times to make sure that your $RANDOM is giving out random values. If it isn't, start a fresh bash session and make sure you're not doing anything to the random variable.
