Wierd IPv6 stuff?

I've just set up my home network with IPv6 which seems to be going swimmingly:

Except...
The above goes to the Internet via a BT Home Hub 5A re-flashed and pressed into service as a dumb VDSL/ADSL Bridge modem (see Ch 9.8).
The above is at a static 192.168.0.10 and does DNS/DHCP from 192.168.0.20 for the network and now the DHCPv6 etc for IPv6 as well, while the bridge modem is at static 192.168.0.1.
So, the above seems to set itself up with a sensible IPv6 address once I set the IPv6 suffix to ::10.
And, that left just the bridge modem without any IPv6 - and, to tidy that up I though to assign a static IPv6 address as it has a static IPv4 address...
Well, I've been fighting to manage that for hours.
Q1 How to set a static IPv6 on OpenWrt?
Frustrated with my progress I thought to run:

root@dslgateway:~# ping6 ::1
PING ::1 (::1): 56 data bytes
ping6: sendto: Network unreachable
root@dslgateway:~# ping -6 ::1
PING ::1 (::1): 56 data bytes
ping: sendto: Network unreachable
root@dslgateway:~#

Hmm, okay...:

root@dslgateway:~# ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1): 56 data bytes
ping: sendto: Network unreachable
root@dslgateway:~# ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1): 56 data bytes
^C
--- 192.168.0.1 ping statistics ---
7 packets transmitted, 0 packets received, 100% packet loss
root@dslgateway:~#

WTF!
Okay then:

root@dslgateway:~# ping 192.168.0.10
PING 192.168.0.10 (192.168.0.10): 56 data bytes
64 bytes from 192.168.0.10: seq=0 ttl=64 time=0.679 ms
64 bytes from 192.168.0.10: seq=1 ttl=64 time=0.673 ms
64 bytes from 192.168.0.10: seq=2 ttl=64 time=0.692 ms
^C
--- 192.168.0.10 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.673/0.681/0.692 ms
root@dslgateway:~#

Well, at least that works!
And, pinging localhost on at 192.168.0.10 works for both IPv4 and IPv6.
Q2 Any ideas what's going on with localhost on my dumb bridge modem?
Q3 Are Q1 and Q2 connected?
Thanks

Please provide output of

ubus call system board

The topics you link refer to ancien% non-official builds, you may have better ipv6 luck with 23.05

Thanks for coming back @brada4:

root@dslgateway:~# ubus call system board
{
	"kernel": "5.4.179",
	"hostname": "dslgateway",
	"system": "xRX200 rev 1.2",
	"model": "BT Home Hub 5A",
	"board_name": "bt,homehub-v5a",
	"release": {
		"distribution": "OpenWrt",
		"version": "21.02.2",
		"revision": "r16495-bf0c965af0",
		"target": "lantiq/xrx200",
		"description": "OpenWrt 21.02.2 r16495-bf0c965af0"
	}
}
root@dslgateway:~#

It is a bit ancient, backup configuration, sysupgrade to v22 then v23.05.3(config migration requires one step at a time)
retry ping -6 localhost

Thanks @brada4 is there such a thing as a 'static' IPv6 address?

Yes, list ip6addr, or the IPv6 Addresses box in Luci. If the overall proto of the interface is not static, you'd need an alias interface.

For administering a modem you can either use the link-local it already has, or assign it a ULA. A GUA is not appropriate for this since you don't want the modem login to be globally reachable.

No idea how you sabotaged your loopback interface, just reset with sysupgrade and it will ping.

1 Like

Thanks @brada4 and @mk24, after sleeping on it I thought to:

root@dslgateway:~# ip addr
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
...

And so:

root@dslgateway:~# ip link set dev lo up
root@dslgateway:~# ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: seq=0 ttl=64 time=0.541 ms
64 bytes from 127.0.0.1: seq=1 ttl=64 time=0.424 ms
64 bytes from 127.0.0.1: seq=2 ttl=64 time=0.422 ms
^C
--- 127.0.0.1 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.422/0.462/0.541 ms
root@dslgateway:~# ping ::1
PING ::1 (::1): 56 data bytes
64 bytes from ::1: seq=0 ttl=64 time=0.833 ms
64 bytes from ::1: seq=1 ttl=64 time=0.497 ms
64 bytes from ::1: seq=2 ttl=64 time=0.496 ms
^C
--- ::1 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.496/0.608/0.833 ms
root@dslgateway:~#

Etc...
Sorted

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