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Standard User Hereisphilly
(newbie) Wed 03-Sep-14 15:56:56
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Connecting VDSL modem to router via powerline, slow internet


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Hi there, I've been referred here by someone on BT's forums, so if anyone can help that would be a massive help! Here's my problem:

I'm experiencing extremely slow internet speeds with my newly rearranged broadband setup, and I really cant figure out why, so any help would be appreciated.

Basically, my 3 story house is wired with ethernet, but only from the 1st floor to the second, and then the 1st floor to the 3rd. My new netgear R7000 router was originally connected to the vdsl modem downstairs, then wired to my htpc, sky box etc, and then connected to another switch upstairs where my home server and PC are located.

Trying to maximise my wireless speed on 5Ghz all over the house Ive swapped the router and switch over, so the router is now on the middle floor, and the switch on the ground. As i've only got 1 cable run from 1st floor to second, I decided to powerline the WAN from the modem upstairs to the router.

I've bought some Zyxel Pla5205 units as the real connection speed, typically around 90mbps, exceeds my infinity connection (sitting at around 65 mbps).

Connecting them up i get a massively reduced internet speed of around 2 mbps

The link rate is good between the two and I've tested the powerline adapters on the LAN only and the sequential throughput i get is 11 MB/s = 88mbps so the adapters are not the limiting factor

Connecting my laptop direct to the modem for testing purposes only, then speedtesting gives my full internet speed, then connecting again through the adapters knocks the speed down massively, so I've identified that its the modem to the powerline adapters thats the issue, but cant figure out why, anyone have any thoughts/advice?
Administrator MrSaffron
(staff) Wed 03-Sep-14 17:25:15
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: Hereisphilly] [link to this post]
 
Are the modem and router the ONLY two devices on the power line network?

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User Hereisphilly
(newbie) Wed 03-Sep-14 18:54:23
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: MrSaffron] [link to this post]
 
In reply to a post by MrSaffron:
Are the modem and router the ONLY two devices on the power line network?

Yeah, I've only got 2 in the entire house, modem is on one and router is in the other on the floor above


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Standard User caffn8me
(knowledge is power) Wed 03-Sep-14 20:14:51
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: Hereisphilly] [link to this post]
 
deleted

Sarah

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If I can't drink my bowl of coffee three times daily, then in my torment, I will shrivel up like a piece of roast goat

Spiders on coffee - Badass spiders on drugs

Edited by caffn8me (Wed 03-Sep-14 20:15:45)

Standard User gah789
(regular) Thu 04-Sep-14 00:21:45
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: Hereisphilly] [link to this post]
 
Your network setup may be the source of the problem. Where is the switch that serves your HTPC and other network connected hardware on the 1st floor in your layout? Your description implies that you have one of the following connections: (i) Router WAN port -> Powerline adapter 1 -> Powerline adapter 2 -> VDSL Modem or (ii) Router WAN port -> Powerline adapter 1 -> Powerline adapter 2 -> Switch -> VDSL Modem. Which is it?

The second will certainly slow things up because the switch won't know where the WAN traffic has to go, so it has to do separate processing for each packet. Even the first may not work if, as is possible, the Powerline adapters operate as mini-switches.

To test your setup, you should bypass the Powerline adapters by using a long Ethernet cable in place of the the Powerline link and test the speed with that setup. Also ensure that there is a direct connection from the Router WAN port to the VDSL Modem. The system should operate at full speed. Then restore the elements of your existing system one step at time until you can identify which step leads to a drastic decline in speed.

The Zyxel PLA5205 units are well regarded and have good performance as you have found. The product description refers to QoS features which suggests to me that they operate internally as switches in managing traffic, so you are putting at least two switches between your router WAN port and the VDSL modem.

I strongly suspect that your original setup - router connected to modem on the 1st floor - is by far the safest layout. In that case you might consider installing a dual band WiFi extender such as the Apple Airport Express on the 2nd floor.
Standard User Hereisphilly
(newbie) Thu 04-Sep-14 07:47:07
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: gah789] [link to this post]
 
In reply to a post by gah789:
Your network setup may be the source of the problem. Where is the switch that serves your HTPC and other network connected hardware on the 1st floor in your layout? Your description implies that you have one of the following connections: (i) Router WAN port -> Powerline adapter 1 -> Powerline adapter 2 -> VDSL Modem or (ii) Router WAN port -> Powerline adapter 1 -> Powerline adapter 2 -> Switch -> VDSL Modem. Which is it?

The second will certainly slow things up because the switch won't know where the WAN traffic has to go, so it has to do separate processing for each packet. Even the first may not work if, as is possible, the Powerline adapters operate as mini-switches.

To test your setup, you should bypass the Powerline adapters by using a long Ethernet cable in place of the the Powerline link and test the speed with that setup. Also ensure that there is a direct connection from the Router WAN port to the VDSL Modem. The system should operate at full speed. Then restore the elements of your existing system one step at time until you can identify which step leads to a drastic decline in speed.

The Zyxel PLA5205 units are well regarded and have good performance as you have found. The product description refers to QoS features which suggests to me that they operate internally as switches in managing traffic, so you are putting at least two switches between your router WAN port and the VDSL modem.

I strongly suspect that your original setup - router connected to modem on the 1st floor - is by far the safest layout. In that case you might consider installing a dual band WiFi extender such as the Apple Airport Express on the 2nd floor.


Sorry if my description wasn't clear, this is what I've got:
VDSL modem-> power line 1-> mains wiring to 1st floor-> power line 2-> router wan port
Connected to the router is a file server and main gaming PC,
Then ive also got an ethernet line already in the walls of the house going downstairs which is router lan-> Ethernet downstairs-> switch -> htpc, sky TV

I had the setup working great for a year with the router connected to the modem on the ground floor, (which served my downstairs stuff) then a hard line upstairs to the switch for the rest of the stuff, but my wireless upstairs isn't as good as I would like it

I've tested my original setup with the power lines on 2 sockets 1m apart and I get the same dropoff in speed compared to the direct modem-> router connection so I'm positive that the powerlines are hurting the traffic between the modem and the router, but not LAN transfers (which implys the units are working OK. This is confirmed by the green link rate indicator on the power lines showing a speed of more than 80mbps)

I've tried with encryption on and off on the power lines and that doesn't seem to help, neither does adjusting the basic qos configs (both the units are set to normal)

What I can't understand is why the power lines are fine for LAN traffic, but in the exact same place in my house, completely tank my internet connection.
Standard User StephenTodd
(experienced) Thu 04-Sep-14 08:29:49
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: Hereisphilly] [link to this post]
 
One thing I found with powerlines is that you should be careful where they are plugged in.
1 - Plugging them into a surge protected extension is an absolute nono.
2 - Plugging them into any extension can cause problems (not always).
3 - Plugging them into one half of a twin socket with computer equipment in the other half can give problems.

3 is a very natural thing to do as it minimizes the distance from the powerline to the equipment it is plugged into, but can lead to much worse performance than you would expect. I didn't believe it till I tried (after seeing somebody else's post on BT forums). If my memory serves me right, I had performance drop from 80Mbps to 10Mbps. Moving to another socket on the same ring restored the 80Mbps; I can't remember if these were the real measured speeds or the speeds reported by the Zyxel utility.

--
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Administrator MrSaffron
(staff) Thu 04-Sep-14 08:32:52
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: Hereisphilly] [link to this post]
 
Some odd interaction with pppoe and packet sizes at a guess.

Using the power line to feed a wireless access point (can have same ssid and passphrase as main router) is best option. Access points start fairly cheap if just 2.4Ghz needed but recommend dual band

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User gah789
(regular) Thu 04-Sep-14 09:04:14
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: Hereisphilly] [link to this post]
 
I was trying to explain your conundrum without going into networking details. Switches and routers are significantly different things. The ports on a router are configured quite separately and may be isolated from other ports for security and other reasons, i.e. with different firewall rules, etc. What most people call a domestic "router" is actually a combination of a switch (connecting the LAN ports) with a single router port (the WAN port). Switches transfer traffic around a single sub-network and do this very fast by holding a map of the IP addresses on the sub-network that can be accessed through the separate ports.

If I am correct in believing that Zyxel Powerline adapters function as switches, then you have introduced a sub-network between your router WAN port and your VDSL modem but one of a kind that the Zyxel adapters don't know how to deal with because the IP addresses of your router port and VDSL port will be on completely different sub-networks. A router configuration can cope with such a link quite easily because it is designed for that purpose, but a dumb switch will just get confused. Your throughput would be even worse if your powerline network had more than 2 adapters.

Understandably, 99.9% of people (including me) don't want to bother with networking arcana like this. I doubt whether you can configure the powerline adapters to act as a pure bridge between your two floors and, even more, it would not be worth the time to try this out. Hence, what you need is a direct cable connection between your router WAN port and your VDSL modem port.

If you do want to experiment, investigate a network setup as follows: Router WAN port -> Switch 1 -> Switch 2 -> VDSL modem, all with cable connections and see how that performs. But why bother, if you are certain that the powerline link is the source of the problem? Further, if you want to learn about the difference between switches and routers, then look at the documentation for Mikrotik's RouterOS (routers) and SWOS (switches). This is unvarnished networking stuff but with a really steep learning curve.

I have over-simplified the situation because it may also depend on how your modem is configured. Some are designed to operate as transparent bridges - decoding the signals and passing the result to your router - while others have an internal bridge and operate as a single port router. My point is that it is necessary to have a combination of networking expertise and knowledge of specific hardware to explain exactly what is going on. I don't think that the issue is worth the effort since it is so easily resolved.
Standard User gah789
(regular) Thu 04-Sep-14 09:15:55
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Re: Connecting VDSL modem to router via powerline, slow inte


[re: MrSaffron] [link to this post]
 
The PPPoE conversion is normally done at the modem, but if not this could easily slow things down drastically depending on how the adapters deal with lost packets since the broadband connection may be forced into frequent retransmission. I have also found that incompatible MTUs can cause various kinds of hard to diagnose problems.
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