Discussion:
No ipv6 address - but only on one machine
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David Rosenstrauch
2017-12-22 17:15:07 UTC
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Having a weird situation going on with IPv6. Every machine on my
network can successfully get an ipv6 address except for one. (My main
server.) What's even weirder is that ipv6 was working on that machine
up until probably about a week ago. Not sure what the problem is, and
hoping someone here might be able to offer a pointer. Here's the
scenario:

1) Wifi router reports an IPv6 address on both the WAN and the LAN
sides. (In the 2607: range.)
2) Mac desktop behind the router successfully gets assigned an ipv6
address.
3) Linux laptop (running Arch) successfully gets assigned an ipv6
address (using NetworkManager).
4) Linux server (also running Arch) does not get assigned an ipv6
address.

The server is using netctl for networking, and its profile includes:

## For IPv6 autoconfiguration
IP6=stateless


Yet for some reason, this machine doesn't get assigned an external ipv6.
Rather it only gets assigned one in the link-local range. (I.e., in
the fe80: range.)

I have to admit this is pretty puzzling. I can't for the life of me
figure out why the server can't get an address. Particular since it was
able to do so successfully probably about a week or so ago.


Anyone have an idea what could have happened here? Has there been some
package update recently that might explain this? Or any pointers on how
I might go about debugging this?

Thanks,

DR
Giancarlo Razzolini via arch-general
2017-12-22 17:43:07 UTC
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Post by David Rosenstrauch
1) Wifi router reports an IPv6 address on both the WAN and the LAN
sides. (In the 2607: range.)
That's a global address range, for sure.
Post by David Rosenstrauch
2) Mac desktop behind the router successfully gets assigned an ipv6
address.
3) Linux laptop (running Arch) successfully gets assigned an ipv6
address (using NetworkManager).
4) Linux server (also running Arch) does not get assigned an ipv6
address.
## For IPv6 autoconfiguration
IP6=stateless
Try using stateful here.
Post by David Rosenstrauch
Yet for some reason, this machine doesn't get assigned an external ipv6.
Rather it only gets assigned one in the link-local range. (I.e., in
the fe80: range.)
Link-local addresses are assigned to any interface when they are created,
regardless of other IPv6 configuration.
Post by David Rosenstrauch
I have to admit this is pretty puzzling. I can't for the life of me
figure out why the server can't get an address. Particular since it was
able to do so successfully probably about a week or so ago.
Anyone have an idea what could have happened here? Has there been some
package update recently that might explain this? Or any pointers on how
I might go about debugging this?
Well, stateless configuration, or SLAAC, relies heavily on ICMPv6 and NDP.
A firewall can block these. If you try to use stateful configuration and it
works, then you might be inadvertently be blocking the packets used on slaac.

Regards,
Giancarlo Razzolini

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