TP-LINK WDR4300 in wireless bridge - connectivity issue

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rekabis
DD-WRT Novice


Joined: 27 Jun 2011
Posts: 9
Location: Canada

PostPosted: Mon Feb 06, 2017 3:43    Post subject: TP-LINK WDR4300 in wireless bridge - connectivity issue Reply with quote
This is driving me bonkers six ways to Sunday.

- TP-LINK WRD4300
- Latest DD-WRT v3.0-r30949

Because of my Apartment situation, I cannot get all Medusa's nest with hundreds of feet of networking cables. Because I have so many business-class and other devices that do not (or cannot) come with wireless cards, it is far cheaper (by at least an order of magnitude) to buy routers, flash them with DD-WRT and turn them into wireless bridges than it is to buy wireless cards for all my machines.

I have a primary router and three bridges. These bridges run the gamut from an old Linksys E3000 to a nice D-Link DIR860L. All except for the problem bridge can connect without any errors. The router and all bridges are running the exact same version of DD-WRT.

The problem bridge connects, but throws RX errors like crazy. I can get an IP address from a domain, which makes sense because it is the router that does DNS, but when I try to ping that IP address it always fails.

I am severely struggling to even understand this issue in the first place. My workstation is behind this bridge. I cannot easily swap this bridge out or switch bridges around. So please bear with me here.

From my workstation, I can ping the bridge. So far, so good. From my workstation, I can ping the router. Awesome. From my workstation, I cannot ping the Internet. Okay, so the problem is at my router, right? ***NO***. If I connect wirelessly to my router (using my iPhone, for example, with data services explicitly shut off), I can ping the Internet. If I log onto my router, I can ping the Internet (Admin->Commands). If I log onto any other bridge, I can ping the Internet. If I log onto any other device attached to any other bridge, I can ping the internet. If I log onto the problem bridge in question, I cannot ping the Internet. I can ping the router, the other bridges, pretty well anything else on the network, but I cannot ping the Internet. And as long as a device isn't behind the problem router, it can also ping the Internet.

I have already wiped all settings and re-created the bridge from the ground up. I have confirmed that all settings between all bridges are 100% identical. I cannot use a backup from another bridge because these are all different makes/models. I have tried resetting the bridge both via software as well as a hard reset. Nothing works.

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teslacoil
DD-WRT User


Joined: 29 Nov 2015
Posts: 117

PostPosted: Mon Feb 06, 2017 17:07    Post subject: Re: TP-LINK WDR4300 in wireless bridge - connectivity issue Reply with quote
rekabis wrote:
The problem bridge connects, but throws RX errors like crazy. I can get an IP address from a domain, which makes sense because it is the router that does DNS, but when I try to ping that IP address it always fails.


Rx errors in Client Bridge mode are normal. I get them too, and they are to be ignored. It's something to do with the Atheros chipset and running in Client Bridge Mode under DD-WRT. It's been discussed numerous time before on this forum. If you switch to WDS the Rx errors will go away, but you have to have compatible chipsets for WDS to work.

Your DNS comes from your main AP and not the CBR, so not sure what you're talking about there. I have two CBR's running on my network which both connect to a main access point and there are 0 problems. Sounds like you have something configured wrong or there is a hardware issue with your unit.

You may try adding the following to the commands box and run it, then click "Save Startup":

Code:
swconfig dev switch0 set enable_vlan 1
swconfig dev switch0 set apply


This is to fix a bug where you can't ping other peers behind the same router in CBR mode. It's not exactly the problem you're describing but you could try running the commands to see if anything changes. If that doesn't work, erase the nvram on the unit before and after flashing to the latest DD-WRT, then reset to defaults with the flash. Follow the instructions to set up the router in CBR mode:

https://www.youtube.com/watch?v=KE1mr-TXUPo
rekabis
DD-WRT Novice


Joined: 27 Jun 2011
Posts: 9
Location: Canada

PostPosted: Fri Feb 24, 2017 5:30    Post subject: Reply with quote
Quote:
Your DNS comes from your main AP and not the CBR


Well, duh. That’s exactly what I said - the bridge is getting the IP address from the router’s DNS, but it is unable to ping that IP address, despite everything else (beside it, not behind it) on the network being able to ping the IP address.

Let’s say I have three bridges - bridge 1, 2, and this problem bridge being bridge 3. I have a router, call it R. I have any number of computers (C), either physically wired to the various bridges or connected wirelessly to R (I have no systems set up as both).

When 3 “goes down”, I can still connect to 3 (even though it is “down”), and from 3 I can ping R, I can ping 1, 2 and any C (both behind it, beside it or behind any other bridge), but I cannot ping anything on the Internet. A ping using a URL gets an IP, but I cannot ping that IP from 3 or any C behind 3.

Being absolutely clear: I can ping both IP and domain name from 1, 2, R and other C, but not 3 or any C behind 3. It’s like C looses the ability to connect to any IP address beyond R, and therefore any C behind 3 also looses that ability. DNS is fine. Great, even. I can get the IP address of any domain I want, even when 3 is “down”, because obviously the issue is with 3 and not R. But I cannot connect to said IP address from 3 or any C behind 3.

This is the very first time in about 3 decades of being on the Internet that I have come across this issue. It is extremely strange. The only resolution is to reboot 3 and keep rebooting it until I can get external ping back. Sometimes I spend the better part of an hour rebooting 3 until it finally begins communicating properly again.

Ideally I would love a script that would be continually pinging an IP, such as 8.8.8.8, and the minute it cannot reach the IP it would automatically reboot the bridge. And once networking came back up, it would start pinging again. And upon four or more failures, reboot the bridge. And so on until pings were successful. That way I could be assured that all I would have to do is wait until the bridge stopped rebooting to know that it was back in functional condition.

Quote:
where you can't ping other peers behind the same router in CBR mode.


This is the exact opposite of the problem I am having. I can still ping anything on the network from any other computer, I just cannot ping anything beyond R from 3 or any C behind 3. Remember: R and any other bridge or C can be pinged perfectly fine.

And yes, this device has been zeroed out to “factory settings” multiple times, and all settings rebuilt from scratch. I have done this enough times that I have set up a fifth bridge (for my printers) completely from memory, without having to refer to docs even once. And it is working flawlessly.

Frankly, I am beginning to suspect hardware failure instead of anything software based.

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teslacoil
DD-WRT User


Joined: 29 Nov 2015
Posts: 117

PostPosted: Fri Feb 24, 2017 10:43    Post subject: Reply with quote
I'm hardwired to a CBR that is wirelessly connected to my main AP. Look, from behind my CBR:

tc@linux:~> ping 8.8.8.8
PING 8.8.8.8 (8.8.8.Cool 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=45 time=81.4 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=45 time=84.4 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=45 time=85.5 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=45 time=80.2 ms
64 bytes from 8.8.8.8: icmp_seq=5 ttl=45 time=80.6 ms
64 bytes from 8.8.8.8: icmp_seq=6 ttl=45 time=83.5 ms
^C
--- 8.8.8.8 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5007ms
rtt min/avg/max/mdev = 80.286/82.658/85.599/2.007 ms

If it's down to one bad CBR, then take that out of the loop and put another CBR in its place. See if the same problem occurs. Put 3 in a location of one of your other CBR's and see if the same problem happens.
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