engage.cloudflareclient.com resolving to ipv4 or ipv6 can change the data center you're connected to

[hparadiz]

Hey so this is kind of a side thing that I discovered when setting up wgcf on my linux box a few days ago. Turns out if the hostname of the end point resolves to ipv4 or ipv6 it can change the data center it uses to connect.

I did a write up here: https://technex.us/2021/02/how-connecting-to-cloudflares-warp-vpn-can-change-your-data-center-depending-on-whether-you-are-using-ipv4-or-ipv6/

Currently for me to force ipv4 I do an nslookup on engage.cloudflareclient.com then I set
Endpoint = engage.cloudflareclient.com:2408 to the ipv4 address to force it to use ipv4.

I figure this might be something people would want as a setting or at the very least be aware of when setting it up.

[ViRb3]

Hey there! Interesting discovery. To make sure we're on the same page, does Cloudflare offer different servers for IPv4 and for IPv6? If that's the case, do we know for sure whether IPv4 or IPv6 offers more (better?) servers?

[hparadiz]

I'm just reporting what I experienced from my location in Hawaii. I was getting the Honolulu datacenter on my Macbook pro using the official client but by default on Linux it was connecting me to LA. Took me a while to figure out how to switch to Honolulu but it only worked when I did an nslookup on engage.cloudflareclient.com and used the ipv4 IP manually. If I stayed on IPv6 it would always route me to LA.

[morpig]

Looks more of an ISP issue to me. Maybe your ISP doesn't peer v6 with CF locally in Hawaii.

[hparadiz]

I have no idea if it's the ISP peering or if CF hasn't deployed an IPv6 gateway to HNL or if even they did but the DNS is returning the wrong IPv6 address (hey it's their DNS!).... who knows. All I know is that the official client somehow deals with it.

Now if I run trace before I start the VPN I get HNL data center. After turning it on with IPv6 I get LAX. After turning it on with IPv4 I get HNL. Maybe it tries both and makes sure it matches the original?

Anyway on Reddit I've also been seeing random reports like this. https://old.reddit.com/r/CloudFlare/comments/lsbbak/warp_routes_me_via_usa/

This user claims they are in Turkey and being routed via LAX. I doubt that is an ISP issue.

[morpig]

yeah, still looks like an isp issue for me. doesn't make sense for cloudflare to deploy v4/v6 warp seperately. i think the client will prioritize v6 > v4 to connect to WARP.

from what i know, warp is only available on several data centers, not all of them. so it does make sense if users in turkey are connecting to LAX.

https://developers.cloudflare.com/warp-client/known-issues-and-faq#why-am-i-not-connecting-to-a-closer-cloudflare-point-of-presence