When booting the bootsrap ISO image the node can succesfully get it's IP address from DHCP:

Nov 22 20:29:32 fedora dnsmasq-dhcp[26419]: 6573570 DHCPREPLY(nat64) fd00:abcd:abcd:fc00::11 00:04:b0:a2:ae:63:26:3e:6a:87:74:60:49:30:85:9b:71:a5 

After rebooting to disk, the node is unable to retrieve it's address. The DHCP server (dnsmasq) respond "no address available"
Nov 22 20:30:37 fedora dnsmasq-dhcp[26419]: 8813127 DHCPREPLY(nat64) 00:03:00:01:52:54:00:8c:1e:63 no addresses available


Unless one is using a very short lease time, the installation will fail. (Default IPv6 lease time is 24 hours ...)

The DHCP server is configured with static reservations only:
> dhcp-range=fd00:abcd:abcd:fc00::,static,64
> dhcp-host=52:54:00:8C:1E:63,[fd00:abcd:abcd:fc00::11],2m

What happens is:
1. The node boots from ISO - this has a DHCPv6 DUID, probably generated from machine-id. It successfully aquires the lease for address 'fd00:abcd:abcd:fc00::11'. This address is now leased to a client with the specific DUID of the ISO image boot.
2. After the ISO did it's work, the node reboots from disk.
3. Node boots from disk, attempts DHCPv6 - now using a different DUID.
4. The server returns "no addr avail" because 'fd00:abcd:abcd:fc00::11' is already leased to a client with a different DUID (the ISO's DUID-UUID most likely).

Proposed solution:
  Make sure the ISO does a "DHCPRELEASE" when powering down, so that the address is free (not-leased) when the node boots from disk to continue installation.

     openshift-install 4.13.23
built from commit 2a5bc79ec57d71969420af6a7043273f90f775a8
release image quay.io/openshift-release-dev/ocp-release@sha256:ca556d3494d08765c90481f15dd965995371168ea7ee7a551000bed4481931c8
release architecture amd64

    100 %

    1. Configure DHCPv6 using dnsmasq with static reservations only. No pool/range.
    2. Example dnsmasq.conf
dhcp-range=fd00:abcd:abcd:fc00::,static,64
dhcp-host=52:54:00:8C:1E:63,[fd00:abcd:abcd:fc00::11]
log-dhcp

     3. Attempt to install SNO following doc[1].

[1] https://docs.openshift.com/container-platform/4.13/installing/installing_sno/install-sno-preparing-to-install-sno.html     

    Installation fails because after booting from disk the node is unable to configure the required IPv6 address. It will retry DHCPv6 process, and recive "no addr avail" until the lease is expired. (default is 24 hours)

    The installer when booted from ISO should ensure to do a DHCPRELEASE, before rebooting to disk.