2

I moved recently and my TP-Link TL-WR841ND v7 with DD-WRT v24-sp2 (11/21/10) std (SVN revision 15778) started to work oddly.

Previously:

The router was connected to another (ISP's) router/modem. The Internet connection ran at 50 Mbps and worked as expected. (40+ Mbps via WiFi, 49+ Mbps via Ethernet.)

Now:

The TP-Link router is connected to a different router/modem (newer model) with the same ISP. The Internet connection 120 Mbps. With a direct connection to the ISP's router via RJ-45 cable, the Internet speed is around 85/10 Mbps with a ping of 8 ms.

However when I connect through the TP-Link, the speed falls dramatically - it never exceeds 10 Mbps and the ping is unchanged. There is no difference if I use RJ-45 (cat6) or WiFi (NG-Mixed, WPA2).

I've tried:

  • Changing WiFi broadcast channel.
  • Using different Ethernet ports in the TP-Link and other RJ-45 cables between the TP-Link and the PC.
  • Setting TP-Link to connect using DHCP.
  • Cloning the PC's Ethernet MAC address.
  • Restoring factory defaults.

I've had no luck. Any ideas?

Gareth
  • 18,809
Piotr Nawrot
  • 184

1 Answers1

2

Did you check if the TP-Link got a full duplex or a half duplex connection on the WAN-port with the modem.

Some providers force full-duplex with their modem and if your TP-Link is at auto negotiate this will fail miserably. Try setting the WAN-port TP-Link to full-duplex.

If the modem is at full duplex and your router at auto negotiate.
you'll get a duplex mismatch with all the troubles with it.

You can set the DD-WRT to full duplex like in the picture below:

enter image description here

Rik
  • 13,309
  • Unfortunately I have no VLANs tab under Setup - is there any other way to force full-duplex on TP-Link? I've updated to DD-WRT v24-sp2 (03/25/13) std - build 21061 - latest compatible with WR841... – Piotr Nawrot Jan 13 '14 at 23:29
  • 1
    Is your connection indeed half duplex? Can you see the duplex state in the status page? I will need to look tomorrow why that page doesn't show for you (don't have access to my DD-WRT at the moment). (And if it is i take it you can't change the duplex setting on the modem to auto.neg.?) – Rik Jan 13 '14 at 23:37
  • I can't change modem's settings. But diagnosis seems right - log after physically reconnecting cables: Jan 14 01:12:39 DD-WRT kern.info kernel: [ 103.680000] eth1: link down Jan 14 01:12:57 DD-WRT kern.info kernel: [ 121.680000] eth1: link up (1000Mbps/Full duplex) Jan 14 01:13:41 DD-WRT kern.info kernel: [ 165.670000] eth0: link down Jan 14 01:14:01 DD-WRT kern.info kernel: [ 185.670000] eth0: link up (10Mbps/Full duplex) Question remains - how to force eth0 to go 100Mbps? – Piotr Nawrot Jan 14 '14 at 00:19
  • Hey, I don't see the VLANs in my old Linksys either. But the WAN-port should be assigned to eth1, not eth0. See here. What is it in yours? If it is eth1 your logs suggest eth1: link up (1000Mbps/Full duplex) which means it is at full duplex (and 1000Mbps needed for the 120Mbps). Not sure about the inner workings of DD-WRT and if eth0 is used for something. – Rik Jan 14 '14 at 09:19
  • I see the TL-WR841ND only has 100Mbps ports (i thought they were 1Gbps ports) so you can't reach the 120Mbps, ever, with this router (if it's also true for the v7) but 50-70Mbps should be reachable. Then everything should settle on 100Mbps Full Duplex. Did you try a 30/30/30 reset? If you connect the computer directly is your computer set at auto.neg. or at hard full-duplex? (what does the link-status say in both cases?) You could also try the original firmware (or other open wrt's, like tomato or openwrt). – Rik Jan 14 '14 at 10:36
  • Sorry for my absence. I tried to setting eth1 as WAN port, changing firmware to stock, changing firmware to Gargoyle - None of it helped. Any other options than 'buy new router'? – Piotr Nawrot Jan 20 '14 at 01:42
  • I'm still puzzled by the eth0: link up (10Mbps/Full duplex). I believe the eth1 (with 1000Mbps/Full duplex) is the connection to your modem (but i'm not completely certain). Can you check the link-speed of the wired connection PC<->TP-Link? Is that 10Mbps or 1000Mbps? How did you set your PC? To auto.neg. or hard on Full-Duplex? Try switching between the auto.neg and 100Mbps/Full duplex in the adapter settings. (1/2) – Rik Jan 20 '14 at 09:08
  • (2/2) Also the 1000Mbps of the eth1. You router doesn't support a 1000Mbps port so why would it be at that speed? If your modem forces connection at 1Gbps (because it is a 120Mbps line) and your router is forced in 1Gbps mode it could also be a problem. But either way... a connection of 10Mbps on eth0 means you can't get speeds over this. So you first need to determine why the eth0 is on 10Mbps. (This could be that your network adapter in the PC is at the wrong setting) – Rik Jan 20 '14 at 09:15
  • 1
    BTW. do you have a 1Gbps network card in your computer (and tested it)? (or could you test with a computer with such a network card?) Just wondering if you can get the 120Mbps your provider is offering with the proper network card. If you do get 120Mbps then it probably is best to invest in a router which can handle it (on the WAN- and LAN-side). (Yours only goes to 100Mbps max. with all the problem it faces if your modem forces a 1000Mbps-FD connection) – Rik Jan 20 '14 at 15:36
  • I have gigabit (AR8131) ethernet card in PC. It's set as DHCP, standard Win7 config. And works fine.
  • I'm certain that eth0 is default WAN port - I physically reconnected cables to generate log file posted above ;-)
  • I switched WAN port from eth0 to eth1 in DD-WRT, but it didn't help.

    • I think that your last assumption is correct - modem forces 1Gbit connection and my poor TP-Link can't handle it no matter how.

    The question is why I get only 87 mbps...

    Anyway - Thanks @Rik for your help so far! :-)

    – Piotr Nawrot Jan 20 '14 at 22:52
  • I'm still puzzled by the fact DD-WRT decides to limit the internal eth0 to 10Mbps (screwing up your whole speed to 10Mbps). But for the direct connection you could try setting your network card to 'hard' Full-Duplex (somewhere in the settings like here). Maybe (if your modem is set at hard-FD) you also get a duplex-mismatch with your direct connection to the PC. (1/2) – Rik Jan 21 '14 at 09:26
  • (2/2) If your provider really can provide the 120Mbps you should see an improvement. Also try to download one of these 1000Mb testfiles to test the speed in IE. Sometimes those speedtest-sites do not give a accurate result – Rik Jan 21 '14 at 09:27