IPv6 issues - uPnP/MTU

[rhammond84]

Have a strange problem that started playing out as images not loading on twitter on Android phone (n.b. Twitter does not use ipv6, but this must be related to some address resolution issues). Other laggs issues were observed.

http://icmpcheckv6.popcount.org/ is not successful (packet fragmentation).

https://test-ipv6.com/ works, but the final test to determine ipv6 provider times out.

Reducing Wan Mtu to 1412 resolves above issues (but creates other issues on the network - unable to access TV service in built apps).

Alternatively, oddly, turning off uPnP resolves above issues... But then clearly I don't have uPnP.

Turning off ipv6 completely removes the laggy address resolution/specific Twitter images issue..... But then I don't have ipv6.

Issue only seems to have been present for the last few weeks. Isp confirm no issues their end. Am struggling to diagnose from above what the actual issue is?

Am using latest gnuton merlin version for Ax82u. Same issue on latest alpha version.

 

[Dedel66]

I suggest you to add some more information about your setup and how do you have internet acces to your ISP (DHCP PPPoE...).
Please add a signatute with these data.

 

[drinkingbird]

Have a strange problem that started playing out as images not loading on twitter on Android phone (n.b. Twitter does not use ipv6, but this must be related to some address resolution issues). Other laggs issues were observed.

http://icmpcheckv6.popcount.org/ is not successful (packet fragmentation).

https://test-ipv6.com/ works, but the final test to determine ipv6 provider times out.

Reducing Wan Mtu to 1412 resolves above issues (but creates other issues on the network - unable to access TV service in built apps).

Alternatively, oddly, turning off uPnP resolves above issues... But then clearly I don't have uPnP.

Turning off ipv6 completely removes the laggy address resolution/specific Twitter images issue..... But then I don't have ipv6.

Issue only seems to have been present for the last few weeks. Isp confirm no issues their end. Am struggling to diagnose from above what the actual issue is?

Am using latest gnuton merlin version for Ax82u. Same issue on latest alpha version.

Why do you need IPv6?

IPv6 relies on path MTU discovery and ICMP to properly set MTU, far more reliant on it than IPv4. This can be problematic if something in the path is blocking ICMPv6. The spec says nothing should, but that is not always the case.

If you absolutely must have IPv6 you need to test to figure out what MTU your ISP supports and set the router to it. Reboot the router after applying the WAN MTU setting so that it gets applied to your LAN interfaces as well and PMTUD will work properly.

But in reality, there is no need for IPv6 unless you have a private WAN IP and need inbound connections (or a couple other scenarios) and you'll have a lot less issues (there are several bugs with IPv6 in various Asus firmwares) if you just leave it off. Do you have a specific need for it?

 

[rhammond84]

WAN connection is 'Automatic IP' - router connected to the ONT. UK FTTP alt net provider (Toob).

IPv6 is 'Native'.

My 'need' for IPv6 is not strong: I'm behind CGNAT and ideally would not pay for static ip and still be able to access my network remotely via IPv6.

My interest for now is more 'what's happened?' - it has been working fine for more than a year. Only activity change on router has been to trial th enew alpha firmware, which I subsequently reverted. To rule this out, I factory reset the router with latest production firmware... And same issue happens with basic default settings.

 

[drinkingbird]

WAN connection is 'Automatic IP' - router connected to the ONT. UK FTTP alt net provider (Toob).

IPv6 is 'Native'.

My 'need' for IPv6 is not strong: I'm behind CGNAT and ideally would not pay for static ip and still be able to access my network remotely via IPv6.

My interest for now is more 'what's happened?' - it has been working fine for more than a year. Only activity change on router has been to trial th enew alpha firmware, which I subsequently reverted. To rule this out, I factory reset the router with latest production firmware... And same issue happens with basic default settings.

Perhaps you had the MTU customized or some other setting tweaked before that got lost. Do you need uPNP? If the issue goes away without it and you don't need it shut it off (safer to map your own ports if you can anyway).

What kind of reset did you do? You can try first doing the GUI one with "initialize all settings" checked, then when that finishes do the hard reset procedure, make sure everything from the alpha firmware is cleared out.

Regardless still a good idea to test and find out the correct MTU for your ISP as you were seeing errors related to fragmentation.

 

[rhammond84]

Mtu was default/blank before (1500). 1412 was highest that would work in testing.

Had completed all resets - software,hard reset with buttons.

As noted, was all working previously for one year +. The alpha firmware load wasn't necessarily the point at which it started failing (don't have definitive record).

Upnp for e.g. a few xboxes on the network.

Ultimately, I can work around all above, but to me something is screwing up in the routing between ipv4 and ipv6.... And I'd like to fix it the cause of possible.

 

[drinkingbird]

Mtu was default/blank before (1500). 1412 was highest that would work in testing.

Had completed all resets - software,hard reset with buttons.

As noted, was all working previously for one year +. The alpha firmware load wasn't necessarily the point at which it started failing (don't have definitive record).

Upnp for e.g. a few xboxes on the network.

Ultimately, I can work around all above, but to me something is screwing up in the routing between ipv4 and ipv6.... And I'd like to fix it the cause of possible.

There is no routing between IPv4 and IPv6. It uses one or the other from end to end, at least assuming your ISP is native dual stack which most are.

How are you testing your MTU?

Could just be that your ISP has messed something up with their IPv6 implementation recently. Maybe you got a subnet that is blacklisted at some sites or something too.

 

[rhammond84]

Wan mtu tested by incrementally reducing until it worked... But as noted, the lower mtu breaks some other stuff on the network.

The uPnP resolution suggests to me the router is doing something it shouldn't do when trying to resolve ipv4 addresses, or ipv6 (am assuming there's no fundamental reason why upnp switched off would have an impact otherwise?).

 

[drinkingbird]

There is no routing between IPv4 and IPv6. It uses one or the other from end to end, at least assuming your ISP is native dual stack which most are.

How are you testing your MTU?

Could just be that your ISP has messed something up with their IPv6 implementation recently. Maybe you got a subnet that is blacklisted at some sites or something too.

That's not a good way to test the MTU, especially since the router has to be rebooted every time you change it to fully take effect. Check Google (or here) for the process to find and set your MTU. Reboot the router after setting and applying it.

 

[heysoundude]

Have a strange problem that started playing out as images not loading on twitter on Android phone (n.b. Twitter does not use ipv6, but this must be related to some address resolution issues). Other laggs issues were observed.

http://icmpcheckv6.popcount.org/ is not successful (packet fragmentation).

https://test-ipv6.com/ works, but the final test to determine ipv6 provider times out.

Reducing Wan Mtu to 1412 resolves above issues (but creates other issues on the network - unable to access TV service in built apps).

Alternatively, oddly, turning off uPnP resolves above issues... But then clearly I don't have uPnP.

Turning off ipv6 completely removes the laggy address resolution/specific Twitter images issue..... But then I don't have ipv6.

Issue only seems to have been present for the last few weeks. Isp confirm no issues their end. Am struggling to diagnose from above what the actual issue is?

Am using latest gnuton merlin version for Ax82u. Same issue on latest alpha version.

What happens if you
GUI > Advanced Settings > LAN > Switch Control
enable Jumbo Frames and Spanning Tree Protocol
and Apply
(with IPv6 enabled/configured?)

 

[drinkingbird]

What happens if you
GUI > Advanced Settings > LAN > Switch Control
enable Jumbo Frames and Spanning Tree Protocol
and Apply
(with IPv6 enabled/configured?)

Those are both for LAN traffic only. STP also has nothing to do with MTU or IPv6.....

 

[rhammond84]

Mtu: yes, by normal test methods (for ipv4 traffic) 1500 is fine.

I understand ipv6 should implement pmtud and so mtu shouldn't really be a consideration. Haven't quite implemented one of the ways to test mtu formally for ipv6 traffic. However, back to original point, this was working previously.... Am still anchoring back to this is the router erroneously trying to route something it shouldn't.

Stp is on. Jumbo frames off.

Hmmmm...enabling jumbo frames seems to resolve the issue too. What's that indicate?

 

[drinkingbird]

Mtu: yes, by normal test methods (for ipv4 traffic) 1500 is fine.

I understand ipv6 should implement pmtud and so mtu shouldn't really be a consideration. Haven't quite implemented one of the ways to test mtu formally for ipv6 traffic. However, back to original point, this was working previously.... Am still anchoring back to this is the router erroneously trying to route something it shouldn't.

Stp is on. Jumbo frames off.

Hmmmm...enabling jumbo frames seems to resolve the issue too. What's that indicate?

Try turning it back off and see if the issue comes back. Maybe the LAN switch somehow got stuck on a strangely low value, though it shouldn't even be possible to set it below 1518, or 1522 on ports with VLAN tags. Jumbo frames should have no impact on your wan traffic, but you do have to pass through the switch to get there. Potentially the switch was at 1518 but the guest or wan VLANs were hitting 1522. Shouldn't really be possible but never know.

More likely toggling it just reset something that had gotten corrupted or messed up.

 

[rhammond84]

Ended up trying some other stuff (rebooting ONT) then all stopped working again even with Jumbo frames enabled.... Feels the firewall or router is filtering stuff erroneously/settings getting stuck.

Latest: I turned off DOS protection in Wan settings. I know there was a historic bug where that was filtering ICMPv6 pings. Turning this off seems to have left all working through the night... But not sure if it's the cause (specifically because I had previously turned it off in testing and it didn't resolve).

I'll stress test today with some other setting changes and reboots and see if it persists.

Have also not yet tried reverting to stock firmware... So will give that a go.

 

[drinkingbird]

Ended up trying some other stuff (rebooting ONT) then all stopped working again even with Jumbo frames enabled.... Feels the firewall or router is filtering stuff erroneously/settings getting stuck.

Latest: I turned off DOS protection in Wan settings. I know there was a historic bug where that was filtering ICMPv6 pings. Turning this off seems to have left all working through the night... But not sure if it's the cause (specifically because I had previously turned it off in testing and it didn't resolve).

I'll stress test today with some other setting changes and reboots and see if it persists.

Have also not yet tried reverting to stock firmware... So will give that a go.

DOS protection is very problematic and could certainly interfere with PMTUD and ICMP.

 

[heysoundude]

Those are both for LAN traffic only. STP also has nothing to do with MTU or IPv6.....

yes yes, but that doesn't necessarily mean that enabling them won't have an effect on how they're implemented in the firmware or how it works. always worth a shot, until it demonstrably interferes, don't you think?

 

[rhammond84]

Turned DoS protection back on alongside a number of reboots... And still seems to be working.

Reluctant to trial more and break it!.... But more thinking this is some configuration hangover.

Will see if it persists...

 

[drinkingbird]

yes yes, but that doesn't necessarily mean that enabling them won't have an effect on how they're implemented in the firmware or how it works. always worth a shot, until it demonstrably interferes, don't you think?

I guess but by that theory you should enable/disable every feature when troubleshooting. All it will do is add more confusion.

 

[heysoundude]

I guess but by that theory you should enable/disable every feature when troubleshooting. All it will do is add more confusion.

I'd agree you're correct, but sometimes, where it might be difficult to pin down/resolve what causes certain issues, the ends justify the approach and note what worked to people higher on the pay scale to work through

 

[rhammond84]

Stopped working again overnight with no changes/reboots.

Really not sure if this is a router issue, a isp issue or a combination of both.

Either way, giving up for now and turning ipv6 off until have a new firmware to test, or some other significant change driving the short term need!