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Cannot reach one specific IPv6 from one specific network (self.sysadmin)

submitted 2 years ago by TwinTurbo to c/sysadmin

9 comments fedilink hide all child comments

cross-posted from: https://lemmy.world/post/224140

My home ISP does CGNAT for IPv4, but provides native IPv6. I can use IPv6 just fine to access most of my resources, except for one specific server. I can access the server over IPv4 from my home network, and either over v4 or v6 from other networks I've tried. But I can't access it over IPv6 from my home network.

What could be the problem here? Where do I begin to diagnose it

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[–] giacomo 3 points 2 years ago (1 children)

How far does a traceroute get you? That could help isolate where the issue may be.

[–] TwinTurbo 4 points 2 years ago (1 children)

I've looked at one, but all that I can tell is I stop reaching things somewhere between my ISP and the datacenter the server is in.

[–] giacomo 5 points 2 years ago (1 children)

I kinda think it may be on the isp then, maybe a v6 routing issue? You could work around with an ipv4 tunnel, then route ipv6 through it. If that's possible, I've never done it haha.

[–] TwinTurbo 3 points 2 years ago (1 children)

Yeah, ISP-related issue is all I can think of. I can connect to the server over v4 no problem, but the broken v6 connectivity to this particular endpoint is strange and nothing I've seen before...

[–] giacomo 3 points 2 years ago

I bet they get less reports on ipv6 issues than with ipv4. I have definitely seen carriers have ipv4 routing issues in enterprise networking.

[–] SheeEttin 3 points 2 years ago (1 children)

Can you test that site from someone else's ISP, and from someone else near you on the same ISP?

[–] TwinTurbo 2 points 2 years ago

From other ISPs it works fine. I haven’t checked from someone else using the same ISP, but that’s a good idea. Thanks!

[–] kinther 2 points 2 years ago (1 children)

Check your ip address config on the destination server. Does it have a public ipv6 address assigned? Does your server routing table have a default route for that ipv6 network? Does your firewall only allow ipv4?

[–] TwinTurbo 3 points 2 years ago

Yes, I can reach the IPv6 on the server from other networks. I don't think it's a firewall issue.