Cannot connect to R7800 at 5Ghz but can to WNDR3700 V4

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keithg
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Joined: 07 Jan 2011
Posts: 53

PostPosted: Sun Jun 09, 2019 3:05    Post subject: Cannot connect to R7800 at 5Ghz but can to WNDR3700 V4 Reply with quote
I have a few devices (all Samsung) which cannot connect to the 5Ghz band on the R7800. The router is running the latest Kong build DD-WRT v3.0-r39855M kongat (05/25/19). The main culprit is a Galaxy Tab S 10.5in. It 'sees' the router. I type in the password and it connects to the router. Tab shows full bars. R79800 Router shows:
Code:
10:30:47:xx:xx:xx ath0   0:11:19   173M   24M   VHT20SGI   -58   -106   48   
84%

I get no internet I have LAN just no internet. I can connect to the router from the tab and anything on my LAN and it is snappy and works. Just no internet. All other devices on the 5Ghz band work fine can connnect to the LAN and also the internet. When I connect to the WNDR3700v4 with the Galaxy Tab S, it works. Same IP just different AP on the same network. I get internet as well as LAN. This is what is reported on the wndr3700v4
Code:
10:30:47:xx:xx:xx   ath1   0:01:01   57M   78M   HT20SGI   -66   -92   26   
68%


Any ideas?
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keithg
DD-WRT User


Joined: 07 Jan 2011
Posts: 53

PostPosted: Sun Jun 09, 2019 13:05    Post subject: Reply with quote
There seems to be some interaction with IPV6 and this device. I recently replaced the WNDR3700V4 which was running BS build R39866 and had IPv6 enabled and did not notice any problems. I replaced it as my gateway with the R7800 and also enabled IPv6. On both routers I used 'DHCPv6 with prefix delegation'. I tried the other options, but was not able to get it to work at all. I am using Comcast/Xfinity as my ISP. I disabled IPv6 and now have full connectivity. It was only this one device that had problems with this setup. All otehr devices (computers, tablets, phones, gaming consoles, IV, etc) had no problems connecting with this set for ipv6 on the R7800 nor with the 3700v4...

Is this a bug of some sort or a corner case with this particular device? I did notice that the 'about device' showed a lot of ipv6 information when I had it connected.
msoengineer
DD-WRT Guru


Joined: 21 Jan 2017
Posts: 1782
Location: Illinois Moderator

PostPosted: Sun Jun 09, 2019 19:26    Post subject: Reply with quote
keithg wrote:
There seems to be some interaction with IPV6 and this device. I recently replaced the WNDR3700V4 which was running BS build R39866 and had IPv6 enabled and did not notice any problems. I replaced it as my gateway with the R7800 and also enabled IPv6. On both routers I used 'DHCPv6 with prefix delegation'. I tried the other options, but was not able to get it to work at all. I am using Comcast/Xfinity as my ISP. I disabled IPv6 and now have full connectivity. It was only this one device that had problems with this setup. All otehr devices (computers, tablets, phones, gaming consoles, IV, etc) had no problems connecting with this set for ipv6 on the R7800 nor with the 3700v4...

Is this a bug of some sort or a corner case with this particular device? I did notice that the 'about device' showed a lot of ipv6 information when I had it connected.


When you switch routers, The cable modem has to be reset, powered off & back on, to issue you a new IP from Comcast. If you want to keep the same IP as you had before, you'll need to clone the mac address from your other router-3700v4. What you describe is likely from not rebooting the modem and so it didn't want to issue an IP to your R7800.

In terms of IPv6, the picture below is all you should need. I run quad 9 for my DNS, but you can use Comcast's DNS if you like:

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keithg
DD-WRT User


Joined: 07 Jan 2011
Posts: 53

PostPosted: Sun Jun 09, 2019 20:18    Post subject: Reply with quote
Thanks. I will try that and see what happens. It is strange that only one device on my whole LAN had a problem, but I guess stranger things have happened. Cannot do it today, but will see and report back.
keithg
DD-WRT User


Joined: 07 Jan 2011
Posts: 53

PostPosted: Fri Jun 14, 2019 1:19    Post subject: Reply with quote
Well, I did that. Unplugged the cable router and rebooted the ddwrt router. I noticed that I got the same ipv4 and ipv6 address. I also noticed that this particular device doe snot connect properly when ipv6 is enabled. It shows a good solid connection, but it is extremely slow and streaming apps refuse to run because the internet connection is so bad. It is strange that it is only this particular device.
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