Native IPv6 for Merlin's Firmware Not Working

[rajl]

Hopefully someone can help me here. I'm not sure whether my problems with configuring IPv6 on Merlin's firmware is user error or a firmware issue, but hopefully someone here can help me.

I am running build 376.47 on my Asus RT-AC66u router. I tried to enable IPv6 by going to the IPv6 tab, selecting "Native" as the implemenation, selected "stateful" for my IPv6 addesses, and followed the defaults. However, after I save these settings, my router does not get an IPv6 address from my ISP (Comcast). Nor does my router provided IPv6 addresses to devices on my LAN, even though I have the IPv6 dhcp functionality enabled.

I had IPv6 working on my old router (a WNDR3700v1) running the native IPv6 stack offered by OpenWRT (Barrier Breaker). It would get an IPv6 from Comcast and issue IPv6 addresses to all devices on my LAN. However, that router died a horrible, grisly death and has been replaced temporarily by the AC66u. Because the only difference in my setup is the replacement of the old Netgear router with a newer Asus router, this confirms that the problem is with the Asus router.

Any help you can provide would be appreciated.

Thanks!

 

[bmn1]

Make sure you enable DHCP-PD.
Reboot modem and router.

 

[Daybreak]

Hopefully someone can help me here. I'm not sure whether my problems with configuring IPv6 on Merlin's firmware is user error or a firmware issue, but hopefully someone here can help me.

I am running build 376.47 on my Asus RT-AC66u router. I tried to enable IPv6 by going to the IPv6 tab, selecting "Native" as the implemenation, selected "stateful" for my IPv6 addesses, and followed the defaults. However, after I save these settings, my router does not get an IPv6 address from my ISP (Comcast). Nor does my router provided IPv6 addresses to devices on my LAN, even though I have the IPv6 dhcp functionality enabled.

I had IPv6 working on my old router (a WNDR3700v1) running the native IPv6 stack offered by OpenWRT (Barrier Breaker). It would get an IPv6 from Comcast and issue IPv6 addresses to all devices on my LAN. However, that router died a horrible, grisly death and has been replaced temporarily by the AC66u. Because the only difference in my setup is the replacement of the old Netgear router with a newer Asus router, this confirms that the problem is with the Asus router.

Any help you can provide would be appreciated.

Thanks!

Howdy,
STEP 1 <--this is a Comcast issue
step 2 <---this is a Comcast issue

What you need to do.
step 1 unplug your cable modem, unplug the router
step 2 go to sleep overnight
step 3 plug in the router and plug in the router.
IPv6 is now working

 

[rajl]

Thanks for the help. It was definitely a Comcast issue that had resolved itself by the next day after powering off both the modem and router and reconnecting everything the next morning. Your advice saved me a lot of frustration.

 

[ScratchMonkey]

I just installed .47 with the dual WAN feature enabled. My 2nd cable modem has IPv6 so I enabled it as rajl describes in the first post. How do I know if it's working? I don't see any status on Secondary WAN with any v6 info. Just the v4 lease. I don't see anything in the system log that looks like a v6 address, so I don't think it got a lease.

If I need the 24 hour thing, is it enough to reboot the modem, or do I also need to leave it powered down 24 hours? What's the actual nature of the Comcast issue?

 

[Keenan]

I'd like to know what is happening with this as well. Like clockwork, my Asus RT-N66 w/Merlin 376.45 drops IPv6 connectivity every day or two(maybe sooner, don't check it every day). A reboot of the router corrects the problem, until abut a day, maybe 2 later, and it loses it again.

If it is a Comcast problem as noted above, can someone post specifically what that problem is so I can push Comcast to fix it on my end?

It doesn't appear to hamper performance in anyway but if it's something that's not working correctly I'd like to fix it.

Thanks

P.S. Did a search for IPv6 and Comcast and this was the first thread that came up.

 

[Deleted member 22229]

I also have a hard time getting a native v6 address but once i get it its all good. For me i boot the modem let it sync then boot the router, normally it does not get a v6 address so i log into the router UI and click reboot this sometimes takes 2 or 3 tries but i get a v6 allocation and it stays working till i have to reboot again for what ever reason. With comcast the lease will expire and renew every two days like clock work.

 

[Keenan]

I also have a hard time getting a native v6 address but once i get it its all good. For me i boot the modem let it sync then boot the router, normally it does not get a v6 address so i log into the router UI and click reboot this sometimes takes 2 or 3 tries but i get a v6 allocation and it stays working till i have to reboot again for what ever reason. With comcast the lease will expire and renew every two days like clock work.

That seems to be my problem, in my case it's not renewing, I have to re-boot the router for IPv6 to become active again.

 

[Deleted member 22229]

That seems to be my problem, in my case it's not renewing, I have to re-boot the router for IPv6 to become active again.

I had that same issue some time ago with a older firmware but it dont seem to be a problem with the last 3 or 4 releases for me anyway. I have no clue if its comcast or Asus or both but IPv6 and Asus routers is sometimes a pita. I just flashed Merlins latest 376.48_1 today and had to go through the same problem i mentioned above to get v6 working but so far its stable. I will know for sure in two days when the lease renews itself. You will also see in your sys log if it was successful or not.

 

[Keenan]

I had that same issue some time ago with a older firmware but it dont seem to be a problem with the last 3 or 4 releases for me anyway. I have no clue if its comcast or Asus or both but IPv6 and Asus routers is sometimes a pita. I just flashed Merlins latest 376.48_1 today and had to go through the same problem i mentioned above to get v6 working but so far its stable. I will know for sure in two days when the lease renews itself. You will also see in your sys log if it was successful or not.

I'll go ahead and update to the latest FW. the reason I haven't to date was that other than the IPv6 problem everything else has worked fine.

Thanks, I'll give your method of sequential booting a try.

 

[Deleted member 22229]

I'll go ahead and update to the latest FW. the reason I haven't to date was that other than the IPv6 problem everything else has worked fine.

Thanks, I'll give your method of sequential booting a try.

Yeah give it a try works for me. As always YMMV.

 

[unsynaps]

Yeah I seem to be having issues with IPv6 after updating to the latest (48_1). Didn't really have problems in previous firmwares.

Will try the long (while sleeping) power off and see what happens tomorrow morning.

 

[neil0311]

Unplugged my modem and router overnight (from 11pm to 7am). Didn't work. Cannot get a v6 address.

My next thought is to clone the MAC address of the old N66U I just replaced to see if that works. I did notice that the v4 address is different than before (as expected) but not sure what effect a different router MAC will have on v6 address.

If that doesn't work, then it's back to stock Asus firmware. This is ridiculous. Only thing I do know anecdotally is that with the N66U I did have v6 issues going past 374.42 and stayed there with no issues. Not sure if the AC68P is able to use firmware that old, but rolling back that far might also be a test. If it works on a completely different router as well, then it's the code not the connection or the router.

 

[Keenan]

I also have a hard time getting a native v6 address but once i get it its all good. For me i boot the modem let it sync then boot the router, normally it does not get a v6 address so i log into the router UI and click reboot this sometimes takes 2 or 3 tries but i get a v6 allocation and it stays working till i have to reboot again for what ever reason. With comcast the lease will expire and renew every two days like clock work.

Following up on this. I updated the FW and used your boot sequence method and for 6 days now I've maintained IPv6 connectivity, so thanks for your input!

 

[knighthawk]

Native-PD and Stateful

If it's any help this is what I had to do to get Native-PD + Stateful working right on my AC68. I don't think the stateful part really has to do with Comcast but I could be wrong. Granted I'm on still on john's 374 fork but the pd+stateful issue I think exists in the 376 line as well.

http://forums.smallnetbuilder.com/showpost.php?p=148258&postcount=574

In addition to the above allowing ipv6 udp port 546&547 (ipv6 dhcp) for fe80::/10 made it pull an ip just fine (on a clean boot) 99.9% of the time without any shenanigans of having to touch\reset my modem, prior to that it was blocking the responses from Comcast.

 

[john9527]

In addition to the above allowing ipv6 udp port 546&547 (ipv6 dhcp) for fe80::/10 made it pull an ip just fine (on a clean boot) 99.9% of the time without any shenanigans of having to touch\reset my modem, prior to that it was blocking the responses from Comcast.

Can you post the specific commands for the above?

 

[owlyn]

I've tried a few things, but what seems to work most of the time is pretty easy. First, disable ipv6 in the router. Unplug the modem, wait 10 seconds, plug it back in, wait for it to finish booting. Then go enable Native ipv6 on the router. You're not done yet. Now, unplug the line connecting the modem and the router ___from the modem side____(yes it matters-don't know why). Wait a few seconds. Plug it back in. Within 10 seconds, you will get an ipV6 address.

Note that this problem didn't start until Firmware .44 or .45 or thereabouts.

 

[knighthawk]

Can you post the specific commands for the above?

Sure.
Goto IPv6 firewall page click + sign and enter a rule with the following info.
Name: CCastDHCP6 RemoteIP:FE80::/10 LocalIP:FE80::/10 ports: 546,547 Proto: UDP

Should ensure requests to dhcp6 servers listening on 547 and responses back from same to the client listening on 546 for fe80::/10 (link-local addresses) make it through. Prior to entering such (and granted the 547 may not really be needed), I was not getting an ip6 address from Comcast and while dropped packet logging was enabled noticed packets from a LL address from source port 547 to 546 were being dropped soon after the DHCP6 requests had been sent. Added the above and rebooted and it started pulling from Comcast without issue - at least during boot up.

The above will result in\is equivalent to the following ip6table rules.
ip6tables -A FORWARD -s fe80::/10 -d fe80::/10 -p udp -m state --state NEW -m udp --dport 546 -j ACCEPT

ip6tables -A FORWARD -s fe80::/10 -d fe80::/10 -p udp -m state --state NEW -m udp --dport 547 -j ACCEPT

 

[bouldernerd]

Thank you Knighthawk. Just tried this and and it worked for me.

 

[john9527]

This is strange as the accept rule for IPv6 DHCP requests is already a standard part of the firewall code. Can someone where @knighthawk's suggestion helped append their ip6tables rules output?