Posso usar apenas IPv6 dentro do meu túnel OpenVPN?

Question

Eu tenho o servidor OpenVPN. Gostaria de saber se posso fornecer apenas endereços IPv6 dentro do túnel, mas não há endereços IPv4?

Eu tentei usar server-ipv6 sem server diretiva, nesta configuração:

port 443
local xx.xx.xx.xx ; my ip

proto tcp-server
dev tun

ca ca.crt
cert server.crt
key server.key
dh dh2048.pem

tls-auth ta.key 0
key-direction 0

topology subnet
client-to-client

keepalive 10 120

auth SHA256
cipher AES-128-CBC

comp-lzo

user nobody
group nogroup

persist-key
persist-tun

verb 3
mute 20

server-ipv6 fde4:1234:5678::/64

push "route-ipv6 fde4:9999::/64" ; server local subnet    

Erro: Options error: --server-ipv6 must be used together with --server

Também tentou substituir server-ipv6 por outras diretivas:

mode server

port 443
local aa.bb.cc.dd ; my ip

proto tcp-server
dev tun

ca ca.crt
cert server.crt
key server.key
dh dh2048.pem

tls-auth ta.key 0
key-direction 0

topology subnet
client-to-client

keepalive 10 120

auth SHA256
cipher AES-128-CBC

comp-lzo

user nobody
group nogroup

persist-key
persist-tun

verb 3
mute 20

tls-server

tun-ipv6
push "tun-ipv6"
ifconfig-ipv6 fde4:1234:5678::1/64 fde4:1234:5678::2
ifconfig-ipv6-pool fde4:1234:5678::72/112
push "route-ipv6 fde4:9999::/64" ; server local subnet

Neste caso, o cliente não pode se conectar com erro (log anexado abaixo)

OpenVPN ROUTE6: OpenVPN needs a gateway parameter for a --route-ipv6 option 
    and no default was specified by either --route-ipv6-gateway or 
    --ifconfig-ipv6 options
OpenVPN ROUTE: failed to parse/resolve route for host/network: fde4:9999::/64
open_tun
CreateFile failed on TAP device: <...>.tap
TAP-WIN32 device [Ethernet 1] opened: <...>.tap
TAP-Windows Driver Version 9.21 
MANAGEMENT: Client disconnected
ERROR: --dev tun also requires --ifconfig
Exiting due to fatal error

Eu não acho que eu realmente precise de IPv6, mas eu apenas me pergunto se isso é possível.