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I had asked similar question here. But instead of reviving it, I thought I would post a new question with additional details. The issue is establishing broadband connection initially. I have a DSL DLink 502T modem which I have been using for long. But now a days, I am having issues while establishing connection. The modem takes several restarts, to establish a broadband connection. The ADSL and PPPoE LED's are off until several restarts, after which they light up. Sometimes it takes as much as 10-12 restarts or even more. Here is what the Modem Log shows when the attempt to connect fails.

MODEM LOG (For failed attempt to establish connection)

oamPingInterval(20)(20)
Valid Configuration Tree
stat successfull for /etc/resolv.conf.
Resolver Polling Timer Started succesfully.
NTP Polling Timer for DHCP Started succesfully.
DSL Polling Timer Started succesfully.
Firewall NAT service started
del_iptable_rules : ppp_name not intact 
Bridge Created: br0
updateall_servers : No children found for conn:
Bridge Created: br1
Bridge Interface Added: eth0
Bridge Interface Added: usb0
DSL Carrier is down
del_iptable_rules : ppp_name not intact 

Once the connection is established it remains stable throughout the day. The Modem then shows following DSL statistics

Modem Status(after connecting)

Connection Status       Connected
Us Rate (Kbps)      510
Ds Rate (Kbps)      2042
US Margin       12
DS Margin       20
Trained Modulation      ADSL_2plus_AnxM
LOS Errors      0
DS Line Attenuation     22
US Line Attenuation     15
Peak Cell Rate      1202 cells per sec
CRC Rx Fast     0
CRC Tx Fast     0
CRC Rx Interleaved      1
CRC Tx Interleaved      0
Path Mode       Interleaved

DSL Statistics
Near End F4 Loop Back Count     0
Near End F5 Loop Back Count     0

I had tried to take help of my ISP Provider but it didn't solve the issue. Any ideas why there is issue establishing a broadband(ADSL PPPoe) connection with the ISP.

1 Answer 1

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Since you have this message

DSL Carrier is down

AND you still manage to connect on occasion I can only guess few causes:

  1. Cable issues - You've got a lose Ethernet cable plug or a wire broken somewhere where it gets moved a lot. If connection error appears and goes away when cable is not being touched ignore this possibility.

  2. Modem Issues - Faulty modem (unlikely, unless you have common power outages) or outdated firmware (very likely if modem is newly acquired or if connection issues are old). In any case update your modem firmware. IF the modem is old and problem is new it is unlikely to be the cause, but if modem is new it just might be the case.

  3. ISP issues - In my experience if modem stays untouched and random modem connection issues appear ISP is usually to blame. Easiest way to check if it's ISP fault (assuming the cables are fine) is trying different modems (borrow one from a friend or neighbor). If another modem connects without issue that indicates Modem (or its firmware) fault if all modems have same issues it indicates ISP fault.

I've helped people with different connection problems (connection to ISP dropping; connection staying, but internet vanishing; no connection at all etc.) a fair amount of times. The cause is generally either ISP, WiFi Quality or users/software overloading the internet / modem bandwidth . In my experience physical faults (like in device or cable) are very rare, and PC software failures are uncommon compared to the 3 I named before.

Anyway, of all those timer ISPs (in several countries) never admitted their issues unless you call them and give them facts that support failure outside of your system. Also, cables outside of your home are not considered your issue if you pay line rental.

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  • I easily eliminate point 1 of your response. Cable cannot be the issue since I don't have to do any adjustment to get the connection and once obtained the connection stays for the whole day. Point 2 can be less likely, as my Modem is old and the connection issue is new. Nevertheless, I will try to see if there is firmware update available for the modem make. Point 3 can be a likely issue but as you said, it has to be firmly supported by facts. But I just forgot to mention another point. I am connecting my PC to modem through a switch. Is there a chance that switch might be faulty?
    – Jatin
    Oct 25, 2014 at 9:42
  • What kind of connection have you got? Could it be DSL by any chance? Also, switch should not cause any issues to the modem connecting to the ISP. You can try taking it out if the chain, just to be safe. Are you having similar troubles connecting PC to modem or connecting to modem's settings page?
    – Zero
    Oct 27, 2014 at 5:51
  • I think connection is DSL (or ADSL). I connected the PC directly to modem without involving switch, and the connection issue still persists. So, switch is not the one causing issues.
    – Jatin
    Oct 28, 2014 at 9:37
  • Given your situation, the best advice I can give you is borrow someone else's modem and test connection (makes sure to back up their settings when you do). If you have problems with a different modem its ISP's fault, otherwise it's the modem. Then replace/troubleshoot the one that's causing issues. By the way, the reason I asked for connection type is DSL/ADSL are known to have their issues due to transmission over phone cables. However, It is probably irrelevant since issues mostly come up in connection quality (i.e. speed, package loss etc.) and rarely impact ability to connect.
    – Zero
    Oct 30, 2014 at 10:34
  • As suspected it turned out to be a Modem issue. I have replaced the old Modem with a new one and the issue seems to be resolved. I am getting a stable connection within a few seconds the modem is turned on.
    – Jatin
    Dec 25, 2014 at 13:17

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