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We have an issue on our ADSL connection, networked to a few (4, sometimes 5 in use at a time) computers, as follows:

  • 1 x Linksys Modem Router - Wireless-N ADSL2+ Modem Router WAG120N
  • 1 x 24 port switch
  • 5 computers connected to the switch via LAN CAT5E cables
  • Another few workstations have wired connections also, but are not in use at the moment (I.e. the wires are there but no PCs).
  • The wireless of the Linksys router is currently NOT in use by anyone. Wireless is still "on" though, unused.

The issue is that our connection keeps dropping. Our computers (mostly on Windows 7, and one on Ubuntu) lose network access, although we still can connect to the Linksys interface 192.168.1.1. The status of the router says "Disconnected" at this time, which means it got disconnected from the internet. The router automatically reconnects after a minute or so. I have pasted below a typical log from the router just before and after the disconnection/reconnection. I have labelled there where the disconnection occured (see below).

We also have an older single port modem-router from D-Link, which does not drop the connections, but has its own problems, such as the internet becomes really slow sometimes. We have called our service provider support who tell us that the phone line up to our premises is fine. They did not check the inside connections though, they just guarantee that the wire uptil the premises is OK. So, we think it's one of the following issues: I) The phone line from the outside to our modem inside (I.e. insider our premises) is faulty, so we need to put in a new/fresh phone line and try this. Noise could sometimes disrupt the connection of course, and one of our guesses is that noise is causing the connection to become slow (old router) or disconnected (new router).

ii) Some issue within our network is another possible cause - on our PCs. We run Avira antivirus and Lavasoft Awaware and Spybot to clean up viruses / spyware etc. and so far Spybot just finds a few browser cookie issues when we run it and cleans them up.

We're lost on how to know exactly what is wrong. Running a tracert on www.Google.com works fine when the connection is up, and doesn't work when the connection is down. For example:

C:\Users\THE>tracert www.Google.com
Unable to resolve target system name www.Google.com.

C:\Users\THE>tracert 192.168.1.1

Tracing route to 192.168.1.1 over a maximum of 30 hops

  1    <1 Microsoft    <1 Microsoft    <1 Microsoft  192.168.1.1

Trace complete.

And when the modem router is connected, the tracert has about 11 hopes. A couple of those are say 106ms and 754ms towards the end, I think because generally our net connections here in Sri Lanka aren't that good! I'm on a 1Mbps line and sometimes get a good download rate, but then again we do have the above issues during office hours. Any help here would be appreciated, I'd like as much feedback as possible before attempting to put in a new phone line to see if that is the issue.

The log from the router:

Fri, 2011-09-09 14:20:34 - Returning UPnPError 714: NoSuchEntryInArray
Fri, 2011-09-09 14:20:34 - AddPortMapping: external NULL:42193 to 192.168.1.30:42193 protocol TCP for: MSNMSGR with timeout:0
Fri, 2011-09-09 14:20:34 - no permission rule matched : accept by default (n_perms=0)
Fri, 2011-09-09 14:20:34 - redirecting port 42193 to 192.168.1.30:42193 protocol TCP for: MSNMSGR
Fri, 2011-09-09 14:20:34 - creating pass rule to 192.168.1.30:42193 protocol TCP for: MSNMSGR
Fri, 2011-09-09 14:20:34 - GetSpecificPortMappingEntry: rhost='NULL' 42193 TCP found => 192.168.1.30:42193 desc='MSNMSGR'
Fri, 2011-09-09 14:20:34 - AddPortMapping: external NULL:42193 to 192.168.1.30:42193 protocol TCP for: MSNMSGR with timeout:0
Fri, 2011-09-09 14:20:34 - removing redirect rule port 42193 TCP
Fri, 2011-09-09 14:20:34 - Trying to delete rules at index 0
Fri, 2011-09-09 14:20:34 - DeletePortMapping: external port: 42193, protocol: TCP
Fri, 2011-09-09 14:20:34 - removing redirect rule port 42193 TCP
Fri, 2011-09-09 14:31:26 - No response to 3 echo-requests
Fri, 2011-09-09 14:31:26 - Serial link appears to be disconnected.
Fri, 2011-09-09 14:31:26 - Enter: tdb_store.
Fri, 2011-09-09 14:31:26 - tdb_store: calling tdb_update.
Fri, 2011-09-09 14:31:26 - Enter: tdb_update.
Fri, 2011-09-09 14:31:26 - Enter: tdb_store.
Fri, 2011-09-09 14:31:26 - tdb_store: calling tdb_update.
Fri, 2011-09-09 14:31:26 - Enter: tdb_update.
Fri, 2011-09-09 14:31:26 - Enter: tdb_store.
Fri, 2011-09-09 14:31:26 - tdb_store: calling tdb_update.
Fri, 2011-09-09 14:31:26 - Enter: tdb_update.
Fri, 2011-09-09 14:31:26 - Couldn't increase MTU to 1500.
Fri, 2011-09-09 14:31:26 - Couldn't increase MRU to 1500
Fri, 2011-09-09 14:31:26 - LCP down.
Fri, 2011-09-09 14:31:29 - Failed to get IP address for interface ppp0
Fri, 2011-09-09 14:31:29 - Failed to get IP address for interface ppp0    
Fri, 2011-09-09 14:31:32 - Connection terminated.
Fri, 2011-09-09 14:31:32 - Connect time 12.1 minutes.
Fri, 2011-09-09 14:31:32 - Sent 626579 bytes, received 2853159 bytes.
Fri, 2011-09-09 14:31:32 - Enter: tdb_store.
Fri, 2011-09-09 14:31:32 - tdb_store: calling tdb_update.
Fri, 2011-09-09 14:31:32 - Enter: tdb_update.
Fri, 2011-09-09 14:31:32 - Doing disconnect
Fri, 2011-09-09 14:31:32 - Exit. **************** [We lost connection here]
Fri, 2011-09-09 14:32:49 - ADSL is connected **************** [We regained connection here]
Fri, 2011-09-09 14:32:55 - Initialize LCP.
Fri, 2011-09-09 14:32:55 - Plugin pppoe loaded.
Fri, 2011-09-09 14:32:55 - PPPoE Plugin Initialized
Fri, 2011-09-09 14:32:55 - Plugin pppoe called. 
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1 Answer

Everything you have said is pretty normal and whilst individual machines may have problems, I doubt that is contributing to the overall issue.

From what you have said, I think it is one of two issues (or possibly a sort of mix):

  1. You have a noisy or bad line. The old router is SNR variable (higher noise, slower speed to stay stable) and the newer router either doesn't use SNR well or isn't fast enough which is causing drops.

  2. The routers are faulty! Check for firmware updates for either, or, buy a more powerful router.

I am leaning a lot more to point 1 as I think it is the most likely issue.

share|improve this answer
    
Thanks very much William, we'll check this. I just found some links on the Linksys WAG120N and a number of people have complained about it - with the connection drops and old functionality. Unfortunately people have said that it doesn't have any SNR data. It looks like I need to try a new line and then try both modems and see if either of them work better. Both routers are up to date on firmware (the Dlink isn't actually but it wasnt upgradable the last time we tried). Any advice of how to tell if any new modem router I purchase in the future is 'good'? Should I mainly check that it uses SNR? –  rishijd Sep 9 '11 at 18:07
    
@rishijd - all I can suggest is to check for reviews –  William Hilsum Sep 9 '11 at 19:47
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