How to access IPv4 at IPv6-only VPS

Background

Here I bought a (almost-)free VPS from euserv, which is IPv6-only VPS.

But, there is still many website only support IPv4, i.e. GitHub.

At last post, we introduce a way IPv6 ssh login from IPv4 net.

At this post, we will introduce a way to access IPv4 net from IPv6-only VPS.

Get config

CloudFlare provide wireguard capability, which basicly is a VPN.

We use WARP-GO to get wireguard config：https://replit.com/@misaka-blog/warpgo-profile-generator

Run it, and get config.

[Interface]
PrivateKey = 12345678901234567890a8FbLUUDord9Pk/y9NYu4G0=
Address    = 172.16.0.2/32
Address    = 2606:4700:110:8c17:4c55:541a:3790:be2d/128
DNS        = 1.1.1.1
MTU        = 1280
[Peer]
PublicKey  = 123456789012345678905/1SUtzH0JuVo51h2wPfgyo=
AllowedIPs = 0.0.0.0/0
AllowedIPs = ::/0
Endpoint   = engage.cloudflareclient.com:2408

For IPv6-only,

1. Peer.Endpoint only could be IPv6 address, which is [2606:4700:d0::a29f:c001].
   You could use dig engage.cloudflareclient.com aaaa to get latest record.
2. We just use CloufFlare to forward IPv4 traffic, so keep AllowedIPs = 0.0.0.0/0, and comment out AllowedIPs = ::/0.

Put configuration into file /etc/wireguard/wgcf.conf

Install dependency and build wireguard-go

# install golang, if you already installed, skip this
cd /tmp && \
  wget https://go.dev/dl/go1.24.1.linux-amd64.tar.gz && \
  rm -rf /usr/local/go && \
  tar -C /usr/local -xzf go1.24.1.linux-amd64.tar.gz

export PATH=$PATH:/usr/local/go/bin

# check golang version
go version

apt install wireguard-tools resolvconf -y

apt install make git -y
cd /usr/local/src && \
  git clone https://git.zx2c4.com/wireguard-go && \
  cd wireguard-go/

make
cp wireguard-go /usr/local/bin/

# check wireguard-go version
wireguard-go --version

Run & Test

Use wg-quick to start WireGuard:

wg-quick up wgcf

Then run ip addr, and we could see a network card named wgcf, which has IPv4 address:

$ curl ipv6.ip.sb
2a:18:6:1::2e
$ curl ipv4.ip.sb
104.28.23.21

At this moment, this VPS could visit IPv6 and IPv4 network.

Auto-Start

Firstly, turn down wgcf manually,

wg-quick down wgcf

After that, try to turn up wgcf by systemd:

$ systemctl status wg-quick@wgcf
Active: inactive (dead)

$ systemctl restart wg-quick@wgcf
$ systemctl status wg-quick@wgcf
     Active: active (exited)

# test network
$ curl ipv4.ip.sb

# mark wgcf auto-start
systemctl enable wg-quick@wgcf