Troubleshooting IPv6 and determining address

bengalih

Regular Contributor
I'm a whiz on IPv4, but I haven't really taken the time to learn IPv6 yet, so this might be a dumb question.
Long story short, due to some problems that were happening on a local system, I disabled IPv6 on my Asus as a test because I was seeing some strange DNS problems on a client.
Turns out this was actually the problem, and once I disabled it on the router my (one) system that was having this problem was ok.
After ensuring that everything else was working, I decided to re-enable IPv6 on the Asus, because it had all been working perfectly fine prior to the reconfiguration required on this one system.

I use the "Native" IPv6 setting, and let me also qualify that I have AT&T Fiber, and I use the wpa_supplicant on the Asus to bypass my AT&T modem and acquire the public IP directly on the Asus.

Prior to disabling IPv6 I went to one of the various IPv6 test sites (i.e. https://test-ipv6.com/) and it successfully passed all tests.
After re-enabling IPv6, it failed (i.e. couldn't detect IPv6).
I disabled and re-enabled IPv6 several times on my router. Each time it failed to report a success.
As a side-note, while my network seemed to get reconnected after every "disable", re-enabling would actually do a full router reboot. I'm not sure if this is normal.

While the "Native" setting was what had always worked for me before, I decided to just test setting it to "Passthrough". This didn't work, but when I then toggled from "Passthrough" back to "Native" everything seemed to work. What was (maybe?) interesting to me is that, as noted above, every time I went from "Disable" to "Native" my router would reboot. This time, when going from "Disabled" to "Passthrough" to "Native" I had no reboots (though the network connection was reset).

So I don't know what is going on with the above. I feel like I have had this issue before where IPv6 was set, but I wasn't able to pass the tests.
So my questions are:
1) Is there some type of delay before IPv6 address will be properly assigned and detected by these test sites? I was monitoring syslog and I didn't really see anything that would indicate it finally kicking in.
2) When I do an ifconfig to see my interface IPs, my eth0 interface shows my IPv6 public IP. The same showed on the main page as my WAN IP, and what is shown when I visit an IP test site. However, while the IP test sites now properly show a v6 address for me, I don't know where I can find that address on the router? The router must be aware of it's own IPv6 address, right? Where is it shown?

thanks
 

bengalih

Regular Contributor
So I think I might be answering my own question here as I poke around some more. Some confirmation would be nice.

1) I still have no answer to as why my router rebooted every time I went from "disabled" to "native", nor why things didn't seem to work until I went from "disabled " to "passthrough" to "native" (and no reboot!) - although maybe that was due to just being impatient (see below).

2) So I realized that the address showing on the IPv6 test sites was the IPv6 address of my client, and not my router. This is a bit confusing to see the public IPv4 as your router IP, but the IPv6 as whatever client the test is running from (i.e. My IPv4 address is always reported as my router WAN address, but my IPv6 address will show as whatever the local IPv6 of that client is).
My basic understanding of this is because IPv6 doesn't use any type of NAT, so the address will always be fully routable.

I think what might have been happening is that my clients were not being given enough time after re-enabling IPv6 on the router to convert from using their Local Link IPv6 address to getting a normal public/global IPv6 address. Because the clients didn't have an address, I was not getting any response from the test site.

I have a few more questions about this, so hopefully someone with good IPv6 knowledge can confirm my thought up to here and I will continue with them...
 

dave14305

Part of the Furniture
I think you’ve got it. Router Advertisements are periodic unless a client solicits one. If a client had no reason to solicit an RA, it would have to wait until the router sends the next RA to know there is a new prefix delegation available to choose an address from.

I’m no expert, but I play one on the Internet.
 

bengalih

Regular Contributor
Thanks. I also figured out how to find my router's WAN IPv6 address - at least from the GUI, it's under System Log > IPv6.
Not sure how to find it from the cli however.
 

dave14305

Part of the Furniture
Thanks. I also figured out how to find my router's WAN IPv6 address - at least from the GUI, it's under System Log > IPv6.
Not sure how to find it from the cli however.
Code:
ip -6 addr show dev eth0 scope global
or
Code:
nvram get ipv6_wan_addr
 

bengalih

Regular Contributor
Code:
ip -6 addr show dev eth0 scope global
or
Code:
nvram get ipv6_wan_addr
Thanks. I tried ip and ifconfig earlier before I figured out the above...since I was searching for my client address I couldn't find it and didn't try again after I realized what the actual WAN IP was.

I'm trying to learn about IPv6 and having a hard time finding a good resource that will walk me through the ground up so what I have been piecing together isn't too cohesive yet in my brain.

I've got some things working now, but will make another post as it is a bit OT.
 

bengalih

Regular Contributor
@dave14305 Oh one other thing. I had another IPv6 issue here:


Someone there called your attention to it a few months ago when I first posted, but I'm not sure you ever chimed in.
If you have any ideas on that thread as to what my problem might be I'd very much appreciate it.
 

lman

New Around Here
I had problems with ipv6 and found a setting that fixed it for me. Tools/other settings/under advanced tweaks and hacks-WAN:Use local caching DNS Server-change it from NO to YES.
 

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