Docsis 3 modem problems (dpc3825)

[JumBie]

Just recently upgraded my internet connection to a 75mbps down and 2up profile. Had to switch over my Docsis 2.0 modem for a Cisco DPC3825 modem, this model is also a wireless router.

Plugged everything in and set it up through a hard wired connection. Consistently getting 75mbps down stable and 2 up. However I noticed this cable modem/router is very unreliable. I have many times where it just drops connection to the internet and network. I can't access the router page or internet during these times. Mind you this is through ethernet and not over wifi, I have yet to try a speed test on my wireless devices but I notice if something connects through wifi my hard wired connection becomes completely unstable.

So I tried to set the modem to bridge move and connect a router to it to see how well it works. I set it to bridge mode and connected my linksys wrt54gs to it, through the linksys router I connected my computer with an ethernet cable. I ran a speedtest and I was getting anywhere from 30-40mbps down with 2 up. This is the same with wireless connections in this configuration. Now I figured this router would be able to handle 75mbps down if it was hard wired, am I correct in thinking so? I'm completely fine with having 30-40mbps down on the wireless connections but for a hard wired connection I find that terrible.

Do you think there is a way to make the DPC3825 stable with both wired and wireless connections? Or should I go the route of bridge mode + router. If so is there a reason the wrt54gs cant support 75mbps down with a wired connection? Or does setting the modem to bridge mode somehow manage to lower the connection speed? Any help would be appreciated.

 

[imagoon]

Smallnetbuilder says that the wrt54g peaked at 53Mb's The GS is the same router with extra ram in it which mostly gives you more room to store NAT data and the like. I would suspect you may be close to the limit of the 200mhz cpu in that router @40mb/s through NAT translation.

http://www.smallnetbuilder.com/lanwan/router-charts/view

 

[ImDonly1]

What are your signal levels on the modem page? Could be signal levels or just the modem itself/isp. I know on comcast they upgraded the firmware of the dpc3008 and it caused frequent reboots for everyone, they had to roll back to the old one. So post signals here or if you are renting the modem, ask for a different one.

As for the wrt54gs try upgrading the firmware or installing dd-wrt on it. Could also be an issue with the mtu setting on the router. Try auto or 1500.

 

[ZeroRift]

I had a similar problem with a wireless N router (not a modem) running in mixed mode where both the wireless and wired connection would simultaneously become unstable.

The fix, for me, was to lock the router to a specific channel. It seems it was switching channels frequently, which would destabilize its WAN link (probably due to cpu load). This was on a 20Mb down / 1.5Mb up, link.

 

[JumBie]

Managed to fix the problem so far.

Turned the modem back into router mode, connected my computer to port 1, and the router to another port, the wire back was plugged into a normal LAN port instead of the WAN port. I disabled the wireless on the modem, and allowed it to act as a modem and wired router. My wired computer is consistently getting 75mbps down and 2mbps up.

The wireless connections are still given an ip address through the modem, because I turned DHCP off on the wireless router. But the wireless connection itself is broadcasted through the linksys router. These connections are getting around 30-40mbps, I'm not sure if upgrading to a wireless N router will give it full speed so I guess it will suffice for now.

Appreciate the quick input and help, I hope this poorly written solution can help others who have the same problem.

 

[VirtualLarry]

Well, I'm glad you found a workable solution, OP.

What I was going to suggest, was a new (-ish) N 300 router, preferably with DD-WRT.

I have 30/25 FIOS, and I don't generally find my N routers running DD-WRT to limit my connection in any way.

But then again, your downstream connection is like 3X what mine is.

I may become eligible for an upgrade to 50/25 in June some time, which would be a nice upgrade. I will see then (if I choose to upgrade), whether or not my current N routers will limit my internet performance or not.


Edit: If I may ask, what was the reason for signing up for such a lopsided internet connection? Is that because the provider doesn't offer a higher upstream?

 

[JumBie]

Well, I'm glad you found a workable solution, OP.

What I was going to suggest, was a new (-ish) N 300 router, preferably with DD-WRT.

I have 30/25 FIOS, and I don't generally find my N routers running DD-WRT to limit my connection in any way.

But then again, your downstream connection is like 3X what mine is.

I may become eligible for an upgrade to 50/25 in June some time, which would be a nice upgrade. I will see then (if I choose to upgrade), whether or not my current N routers will limit my internet performance or not.


Edit: If I may ask, what was the reason for signing up for such a lopsided internet connection? Is that because the provider doesn't offer a higher upstream?

This cable company has a monopoly over the entire east coast of Canada. Its pretty much the fasted download/upload you can get with a cable company in this region. However there is Fibe internet which is the new type of internet the major competitor is pushing which carries faster upload along with download. The only downside being that the internet shares bandwith with the tv boxes that the company provides so if your using the tv and internet at the same time you will notice slowdowns, not my cup of tea.

www.rogers.com - Major internet provider
www.bell.ca - Major DSL/FIBE provider

 

[VirtualLarry]

However there is Fibe internet which is the new type of internet the major competitor is pushing which carries faster upload along with download. The only downside being that the internet shares bandwith with the tv boxes that the company provides so if your using the tv and internet at the same time you will notice slowdowns, not my cup of tea.

That's why my FIOS is 30/25. I pay for 25/25, and Verizon gives me an extra 5Mbit/sec on the download, to offset the bandwidth taken up by the VOD features on the STB. But when I'm not using the VOD, I get that bandwidth available for my general internet usage.

Perhaps your fiber provider does something similar? TBH, I would probably choose fiber, over cable, for the symmetrical bandwidth, even if you did lose a little of it to VOD features.