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Standard User Ignitionnet
(knowledge is power) Tue 17-Dec-13 21:32:31
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TP-Link TL-ER5120 Load Balancing Router

[link to this post]
Quick warning,

Anyone thinking of buying this guy to use to load balance a couple of FTTC lines I'd advise not to.

From my provisional testing it appears to use 50-55% of CPU routing approximately 60Mbit via PPPoE, this neither load balancing or using any of the rate limiting, QoS, firewall or application level features.

TP-Link claim an IP throughput of 350Mb/s for this device and I did ask their support team directly whether the device could handle 160Mb/s of PPPoE and was informed that it could.

The evidence so far says that it will won't make 120Mb/s if it's having to load balance as well. I'll confirm once both lines are in.

Just as well I kept the packaging.
Administrator MrSaffron
(staff) Tue 17-Dec-13 22:43:11
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Re: TP-Link TL-ER5120 Load Balancing Router

[re: Ignitionnet] [link to this post]
PPPoE handling also been an issue for some other routers reducing throughput. Seem to recall someone with FTTP moaning of this on a 330 Mbps line using an RT-N66U

Andrew Ferguson, [email protected] - formerly known as
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User BatBoy
(legend) Tue 17-Dec-13 22:47:02
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Re: TP-Link TL-ER5120 Load Balancing Router

[re: MrSaffron] [link to this post]
Yeah, you really need pfSense on a PC to supply sufficient horsepower.


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Standard User Ignitionnet
(knowledge is power) Wed 18-Dec-13 10:50:45
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TP-Link Response

[re: Ignitionnet] [link to this post]
Dear Carl,

Thank you for choosing TP-LINK, This is Dylan from TP-LINK Technical Support.
Our technican tested that it is capable for your application .Don't worry about that .

Best Regards

We'll see.
Standard User Ignitionnet
(knowledge is power) Wed 18-Dec-13 12:42:21
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Better Idea

[re: Ignitionnet] [link to this post]
Very busy with the day job but when I have the time I'm gong to connect this guy to my test server and run some proper throughput tests under controlled conditions.

Say 100 TCP connections and 160Mb/s of throughput should work.
Standard User Ignitionnet
(knowledge is power) Wed 18-Dec-13 13:30:09
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Re: TP-Link Response

[re: Ignitionnet] [link to this post]
I sent the following to them, which may or may not give them a moment of pause:

Thank you Mr Zhang,

When time permits I will conduct my own testing using my VMWare server and iPerf.

I will update you if it doesn’t perform as expected.

My testing conditions will be:

160Mb/s downstream throughput.
TCP acknowledgements only upstream.
100 active TCP sessions.
2 x PPPoE WAN circuits, MTU 1492
Simple NAT between LAN and WAN
Firewall features *off*
Bandwidth Control *off*
Using WAN0 and WAN1, load balanced via Application Optimized Routing.

May I please ask about the load balancing methodology you use?

Application Optimized Routing – does this ensure that anything with the same source and destination IPs and ports remains on a single WAN circuit, or does it use IPs only, or perhaps destination IP and port?

Bandwidth Based Balance Routing – I’m guessing this is for use only in Non-NAT environments where the source iP and port would be those of the original client machine rather than the IP of the WAN interface on the TP-Link?

With best regards,
Standard User t1mb0
(newbie) Wed 18-Dec-13 19:23:23
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Re: TP-Link Response

[re: Ignitionnet] [link to this post]
Where did my post go?? (hope this doesn't show twice..)

I have just got one of these TP Link Gb routers set up tonight with 4 VDSL modems which are connecting around 30Mb each (Bit low but better than our previous connection by far)

I was really excited for a moment, I was downloading some LEGAL ISO's through P2P as tests and didn't reach more than 6.5 MB per second with around 40-80 connected peers (is that about 60Mb?). It seems to build up then slow way down to 2-3MBs then rise up again but mostly stayed about 4-5MBs. Either way it didn't seem very stable but still I downloaded 8 GB in less than 1/2 an hour or so!!!. Don't really know if that is a valid test . I thought perhaps my P2P client is having problems (Transmission in Ubuntu). But seem to think it could be the router.

I first set up each WAN port as static IP's and each router as the gateway. Then I tried the PPPoE passthrough mode expecting an increase in performance. I didn't get much. instead I got many fragmentation errors. I would like to find the right MTU settings, I was using 1492, then changed it to 1480, both were getting fragmentation, (1-3% or less though)

I tested things like Skype and did many speedtest's from which all worked great in fact, each speed test would only use one WAN port so I got 30Mb consistent speed tests which was sort of expected. but they didn't dip or slow down. I'm thinking that perhaps when many users are logged on they will not notice the issues I had it's just I'm worried that the full throughput of 120Mb will not be utilized...

I would like to know how to test it a bit better and what settings to use or play with, although it's a bit hard with only one PC at the moment. I would like to think I can make the most of all 4 30Mb connections at least, seeing as they're promising 360MB 'Natted' throughput. I don't really want to have to use another firewall in a PC as this would be so sweet it if just worked wink

I am also going to be using ZeroShell as my main firewall which will use the TP Link as it's gateway for 100 od users and try and not use any Nat on the TP Link. Although I don't really understand how the load balancing works and whether or not it requires to run with NAT... It shoudl be possible to have NAT & DHCP pass through the Zeroshell with some messing around I think? This is for a WISP, using long range ubiquiti gear.

Whats your thoughts?


Standard User Varlot
(newbie) Wed 18-Dec-13 21:51:06
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Re: TP-Link TL-ER5120 Load Balancing Router

[re: Ignitionnet] [link to this post]
Its also not ideal for gaming (yes, I know that's not really what its meant for, but still..)
I had a cable connection and an ADSL2 connection routed through this and regardless of which connection was used or how the router was set up I couldn't get an "open" NAT on xbox live
uPnP, port forwarding, port triggering, none of it worked to give an open connection

Using the router for bandwidth throttling, routing designated machines to one connection or another, QoS, port forwarding/triggering and various other options I never saw the CPU usage above 5% (even when it was set up with load balancing it didnt go above about 10% but that completely wrecked the connection for gaming making live kick me offline every few minutes)
That wasn't with PPPoE set up.

I could easily max out the 100Mb cable connection with torrents and still use the second connection (19Mb sync) for browsing, streaming and gaming (but not hosting games due to the connection not being open) without a hiccup.
It was also pretty slick for failover (not that that works for gaming either) and seemed to re-establish connection quite quickly when restored.
Ideal for keeping the missus online when I was working away

This has now been retired from service as dual WAN is no longer required but in general it was a lot better than the ISP provided routers for the vast majority of tasks even when being used temporarily as a single WAN router and it never needed a reset once it was up and running. It just worked.
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