RT-N66U Router not connecting to Internet ?

[ahmadka]

Hi guys .. So I recently switched to Merlin 374.41 FW like 1-2 weeks ago (first time trying out a custom FW) .. Till about 3 days ago everything was working fine .. Then since about 3 days, I haven't been able to connect to the internet when going through the RT-N66U .. However, if I directly connect my laptop to the modem (which the router connects to too) via an Ethernet cable, I am able to access the Internet .. But the router can't seem to access the internet, or even the ADSL modem ..

I've tried rebooting the router once, but that didn't help ..

Also, the weird thing is that if I have an endless ping running, there are a few moments in between when the router CAN access the internet, and can also access the ADSL Modem .. Both happen at the same time ..

In the screenshot below, I have two endless pings running, one for pinging Google DNS (to verify internet connectivity), and one for pinging the ADSL modem .. Both don't generally work, but when they do, they do together but only for a moment ..

So what could be the cause ?

 

[ColinTaylor]

Remove any custom scripts/configs you have in /jffs and reboot. If you still have problems show us the system log of the router after its rebooted.

 

[TonyH]

Hi,
Simple thing first. Tried a different CAT cable?

 

[ahmadka]

Remove any custom scripts/configs you have in /jffs and reboot. If you still have problems show us the system log of the router after its rebooted.

I don't have any custom scripts/configs added. I just restarted the router again, and have attached the System Log so far (kind of long even though I just rebooted - won't let me post here due to character limit) ..

 

[ahmadka]

Hi,
Simple thing first. Tried a different CAT cable?

Just tried that, and it didn't help. I didn't expect this to work though because the Ethernet cable I've put in my house for internal networking was all high grade stuff, and all internal networking is still working fine ..

I also tried connecting to the Internet through the Router, but using Ethernet instead of Wifi .. Same result ..

 

[ColinTaylor]

I don't have any custom scripts/configs added. I just restarted the router again, and have attached the System Log so far (kind of long even though I just rebooted - won't let me post here due to character limit) ..

I can't see anything wrong in the log. What do you get if you telnet/ssh onto the router itself and enter:

# ping 8.8.8.8
# netstat -rn
# ifconfig -a

 

[ahmadka]

I can't see anything wrong in the log. What do you get if you telnet/ssh onto the router itself and enter:

# ping 8.8.8.8
# netstat -rn
# ifconfig -a

Okay, I enabled SSH on the router, then connected via SSH. Again I saw the same lossy ping as before. Here are the full results:

login as: admin
admin@192.168.1.1's password:


ASUSWRT-Merlin RT-N66U_3.0.0.4 Fri Apr 18 19:31:25 UTC 2014
admin@RT-N66U:/tmp/home/root# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: seq=58 ttl=42 time=194.223 ms
64 bytes from 8.8.8.8: seq=59 ttl=42 time=194.377 ms
64 bytes from 8.8.8.8: seq=60 ttl=42 time=208.409 ms

--- 8.8.8.8 ping statistics ---
104 packets transmitted, 3 packets received, 97% packet loss
round-trip min/avg/max = 194.223/199.003/208.409 ms

admin@RT-N66U:/tmp/home/root# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.10.10.1      0.0.0.0         255.255.255.255 UH        0 0          0 eth0
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 br0
10.10.10.0      0.0.0.0         255.255.255.0   U         0 0          0 eth0
127.0.0.0       0.0.0.0         255.0.0.0       U         0 0          0 lo
0.0.0.0         10.10.10.1      0.0.0.0         UG        0 0          0 eth0
admin@RT-N66U:/tmp/home/root# ifconfig -a
br0        Link encap:Ethernet  HWaddr D8:50:E6:AD:9D:18
           inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:36537 errors:0 dropped:0 overruns:0 frame:0
           TX packets:31857 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:5036873 (4.8 MiB)  TX bytes:24040192 (22.9 MiB)

eth0       Link encap:Ethernet  HWaddr D8:50:E6:AD:9D:18
           inet addr:10.10.10.2  Bcast:10.10.10.255  Mask:255.255.255.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:30808 errors:0 dropped:0 overruns:0 frame:0
           TX packets:25234 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:8358243 (7.9 MiB)  TX bytes:5061618 (4.8 MiB)
           Interrupt:4 Base address:0x2000

eth1       Link encap:Ethernet  HWaddr D8:50:E6:AD:9D:18
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:28725 errors:0 dropped:0 overruns:0 frame:373
           TX packets:38882 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:4394094 (4.1 MiB)  TX bytes:25384041 (24.2 MiB)
           Interrupt:3 Base address:0x8000

eth2       Link encap:Ethernet  HWaddr D8:50:E6:AD:9D:1C
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
           Interrupt:5 Base address:0x8000

lo         Link encap:Local Loopback
           inet addr:127.0.0.1  Mask:255.0.0.0
           UP LOOPBACK RUNNING MULTICAST  MTU:16436  Metric:1
           RX packets:611 errors:0 dropped:0 overruns:0 frame:0
           TX packets:611 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:119099 (116.3 KiB)  TX bytes:119099 (116.3 KiB)

vlan1      Link encap:Ethernet  HWaddr D8:50:E6:AD:9D:18
           UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
           RX packets:9386 errors:0 dropped:0 overruns:0 frame:0
           TX packets:9605 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:1994709 (1.9 MiB)  TX bytes:2831077 (2.6 MiB)

admin@RT-N66U:/tmp/home/root#

 

[ColinTaylor]

The router looks fine. Everything points to a problem with your ADSL modem. It seems to be down most of the time and when it is up your ping times to google are horrible. That suggests to me that you have a noise problem on your phone line which maybe causing your modem to continuously re-sync.

Can you see the WAN port going up and down in your logs?

# grep -i wan /tmp/syslog.log

Are there any logs on the ADSL modem that you can look at?

 

[ahmadka]

Alright, so I have some more info to report. I sort of got it working with a workaround, but still no actual fix.

I actually have two phone lines in my house, and both of them have separate internet connections on them. Both internet connections are from the same company, same package, and so have the exact same speeds, etc. However they use slightly different modems, but both have roughly the same feature-set .. I treat one of them as a primary, and the other as a slave, in case the primary goes down for some reason ..

So I tried connecting the router to my slave phone line's modem, and now the router seems to work fine ... I can access the internet and everything ..

However, when I connect it back to my primary modem, it still behaves just like above ..

However still, if I connect my laptop directly to my primary modem, again it works fine .. No problems whatsoever ..

So I can't really say for sure where's the problem .. Because if the modem was the problem, then it shouldn't have worked when I connected my laptop directly to it, right ?

Both the router and the primary line's modem don't seem to like each other .. Connect either to anything else, and they work ..

There is a System Log feature in my primary modem, but I can't get it to work .. No matter what log level I set, it just shows one line:

Jan 1 00:00:15	syslog	emerg	BCM96345 started: BusyBox v1.17.2

Also, ping times shown in that picture are normal for my geographical region and ISP .. Both my phone lines have those same ping times to Google DNS .. The phone lines are also working fine with good SNR's, especially the primary line .. I made sure of that when they were installing the wires in my new house ..

 

[RMerlin]

Alright, so I have some more info to report. I sort of got it working with a workaround, but still no actual fix.

I actually have two phone lines in my house, and both of them have separate internet connections on them. Both internet connections are from the same company, same package, and so have the exact same speeds, etc. However they use slightly different modems, but both have roughly the same feature-set .. I treat one of them as a primary, and the other as a slave, in case the primary goes down for some reason ..

So I tried connecting the router to my slave phone line's modem, and now the router seems to work fine ... I can access the internet and everything ..

However, when I connect it back to my primary modem, it still behaves just like above ..

However still, if I connect my laptop directly to my primary modem, again it works fine .. No problems whatsoever ..

So I can't really say for sure where's the problem .. Because if the modem was the problem, then it shouldn't have worked when I connected my laptop directly to it, right ?

Both the router and the primary line's modem don't seem to like each other .. Connect either to anything else, and they work ..

There is a System Log feature in my primary modem, but I can't get it to work .. No matter what log level I set, it just shows one line:

Jan 1 00:00:15	syslog	emerg	BCM96345 started: BusyBox v1.17.2

Also, ping times shown in that picture are normal for my geographical region and ISP .. Both my phone lines have those same ping times to Google DNS .. The phone lines are also working fine with good SNR's, especially the primary line .. I made sure of that when they were installing the wires in my new house ..

Does your modem report the SNR and attenuation values of your line? If they do please post them here, I'd be able to tell you if your stats are normal.

 

[jlake]

A failing adsl modem will do strange things. In the past, I've spent several hours troubleshooting (and pointing fingers at the provider....oops), only to find out that my DSL modem was failing.

If your cat5e/cat6 cables are good, and your filters are good, it's probably the modem since you've somewhat isolated it.

 

[ahmadka]

Does your modem report the SNR and attenuation values of your line? If they do please post them here, I'd be able to tell you if your stats are normal.

Sure. Below are my stats (left numbers are downstream, right ones are upstream):

Primary Phone Line's Modem (which is problematic):

SNR Margin (dB): 24.6 10.8
Attenuation (dB): 33.5 19.0
Output Power (0.1 dBm): 196 124
Attainable Rate (Kbps): 14716 1086

Slave Phone Line's Modem:

SNR Margin (1 dB): 23.4 10.0
Attenuation (1 dB): 32.5 17.5
Output Power (1 dBm): 19.7 12.4
Attainable Rate (Kbps): 15316 1078

Both lines are 4 Mbps connections. Stats look fine to me more or less.

 

[ahmadka]

A failing adsl modem will do strange things. In the past, I've spent several hours troubleshooting (and pointing fingers at the provider....oops), only to find out that my DSL modem was failing.

If your cat5e/cat6 cables are good, and your filters are good, it's probably the modem since you've somewhat isolated it.

The modem in question has only been used for like 2-3 months .. Plus, the oddest thing is that when I directly connect my laptop to the modem, the internet working fine .. no issues at all whatsoever ..

I can call the phone company and ask them to replace the modem, but they will need definite evidence which confirms that the modem is faulty. Because right now they can just say that it's my router which is faulty, because my laptop works fine with the modem ..

 

[ColinTaylor]

Plus, the oddest thing is that when I directly connect my laptop to the modem, the internet working fine .. no issues at all whatsoever ..

That is indeed very odd. The only thing I can think of (unlikely though it is) is that your ISP is blocking the ASUS because the MAC address has changed recently (from the one in your laptop).

Try turning off the modem and the router for an hour. Then turn on the modem, wait 5 minutes and then turn on the router. Any change?

PS I'd still like to see the output of this command after the router's been up for an hour. Just to eliminate a physical link problem.

# grep -i wan /tmp/syslog.log

 

[sinshiva]

+1 for a failing modem. also had one fail on me; they seem to exhibit weird behavior when doing so.

 

[RMerlin]

Sure. Below are my stats (left numbers are downstream, right ones are upstream):

Primary Phone Line's Modem (which is problematic):

SNR Margin (dB): 24.6 10.8
Attenuation (dB): 33.5 19.0
Output Power (0.1 dBm): 196 124
Attainable Rate (Kbps): 14716 1086

Slave Phone Line's Modem:

SNR Margin (1 dB): 23.4 10.0
Attenuation (1 dB): 32.5 17.5
Output Power (1 dBm): 19.7 12.4
Attainable Rate (Kbps): 15316 1078

Both lines are 4 Mbps connections. Stats look fine to me more or less.

Your Attenuation is a bit high (meaning you are far away from the remote/CO), but it should still be good enough for a 4 Mbits connection (as confirmed by your attainable rates).

The SNR looks good (but not great).

Have you tried just swapping modems? I've dealt with a lot of DSL issues that were caused by modems, sometimes the modems were only 2 or 3 years old. Lots of junk being sold I'm afraid

I assume you also swapped the Ethernet cable between the modem and the router?

 

[Alek]

It does sound like the modem, but if I were you I'd make 100% sure my cabling was good before pronouncing it dead. Also maybe see if there's anyone nearby with a spare modem to swap in and test.

 

[ahmadka]

Okay, I may have found the cause ..

My Router (RT-N66U) was acting as a DHCP server, with the 192.168.1.x scheme. My modem however was using 10.10.10.x scheme, but the only device connected to it was my Router ..

Today I called the cable guy, and I tried out several different modems (connected multiple laptops directly to the modem through Ethernet) .. All of them worked fine, until I switched the modem to 10.10.10.x scheme .. When I did this, I saw mixed results .. Some devices were able to ping the modem (@ 10.10.10.1), while others weren't able to .. Also, pinging between devices was confusing too .. Like Laptop A could ping Laptop B, but Laptop B could not ping Laptop A back, etc ... All sorts of weird things ..

Then I thought that maybe 10.10.10.x is not a suitable IP scheme for my network, so I switched to 10.0.0.x, and so far all connected devices are able to ping the modem (@ 10.0.0.1), including the router, and the devices behind it ..

So the culprit probably was the 10.10.10.x IP scheme which the modems didn't seem to like .. I remember reading about different types of IP Classes, but I never thought it would come back to haunt me, lol.

 

[ahmadka]

What do you guys think about the above stated fix ? Is that a practical reason which can explain the behaviour I was seeing before ?

 

[ColinTaylor]

What do you guys think about the above stated fix ? Is that a practical reason which can explain the behaviour I was seeing before ?

I can't see that it makes any sense, but if there's some bugs in the modem's firmware it wouldn't necessarily have to make sense.

I am very confused about your modem though. I'd assumed it was just a modem. i.e. there was one socket (RJ11) that connected to the phone line and a second socket (RJ45) that connected to your router. No other sockets. However, you talk about connecting two computers to it at the same time and then pinging each other. This implies that there is more than one RJ45 socket. If this is the case then it can't just be a modem, it must be a switch or router as well!

What is the make and model of your modem?

If it is a router/modem combination (very common) are you running it a specific mode. i.e. is it running as a router or is it in bridge mode? When a router is put into bridge mode one of the LAN sockets becomes the connection to the internet and the other LAN sockets are disabled. You can't have more than one device directly connected to the internet in bridge mode. Maybe that is why you were having problems trying to connect two computers at once.

At the end of the day, if you've found a combination that works that's all that matters.