While deploying condev-monitor, I bought a low-cost VPS to save money. In actual use, I found it was IPv6-only, which directly caused the next issue: services that only provide IPv4 endpoints could not be reached.

The most obvious symptom was this: after installing Git, cloning a private Alibaba Cloud Codeup repository failed with fatal: unable to access .... Accessing other public internet resources also failed.

Investigation Process

1. Tried Git over SSH first (failed)

I first switched to SSH in the usual way and configured keys:

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
cat ~/.ssh/id_rsa.pub

After adding the public key to Codeup, cloning over SSH still failed. This suggested the issue was probably not account permission or key configuration.

2. Check DNS and the target service's IPv6 support

nslookup codeup.aliyun.com
dig codeup.aliyun.com AAAA
host codeup.aliyun.com

Results:

  • nslookup returned an A record (IPv4)
  • dig AAAA returned no record (no IPv6)

Conclusion: codeup.aliyun.com has no usable IPv6 endpoint.
So direct access fails on an IPv6-only server.

Solution: Add IPv4 outbound capability to an IPv6-only server

I chose Cloudflare WARP as an outbound proxy. It tunnels outbound traffic so the server can access IPv4 resources (for example Codeup, GitHub, and Docker Hub).

This does not change inbound behavior:

  • SSH over IPv6 continues to work
  • IPv6 services exposed by the server are not affected

1. Install and enable WARP, then route Git through WARP

curl -fsSL https://pkg.cloudflareclient.com/pubkey.gpg | sudo gpg --yes --dearmor --output /usr/share/keyrings/cloudflare-warp-archive-keyring.gpg
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/cloudflare-warp-archive-keyring.gpg] https://pkg.cloudflareclient.com/ $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/cloudflare-client.list
sudo apt update
sudo apt install -y cloudflare-warp

warp-cli register
warp-cli set-mode proxy
warp-cli connect
git config --global http.proxy http://127.0.0.1:40000

There were many errors, so I switched to the one-click script approach.

3. Use a one-click script to quickly set up dual outbound paths

To get "native IPv6 + IPv4 tunnel" outbound paths faster, use fscarmen's one-click script:

wget -N https://gitlab.com/fscarmen/warp/-/raw/main/menu.sh && bash menu.sh

Verification

curl -4 ip.sb
curl -6 ip.sb

If you get both IPv4 and IPv6 results, the server now has dual outbound capability.

Final Status

  • SSH still runs on native IPv6 and remains stable
  • Access to IPv4-only code hosting and registry services is no longer blocked
  • The IPv6-only VPS can now handle normal development and deployment tasks