Cisco-LinkSys E900: WAN to LAN Performance Mystery

[Sujay Sarma]

Hello,
I am purely talking about *wired* LAN performance in my question. Wondering if anyone here have ideas to help before I throw it away in frustration.

Here's the scenario:
I have a 100 Mbps full duplex Ethernet internet connection from my ISP. Previously, speed tests (speedtest.net) have given consistent results in the 94+ Mbps range in both directions. I have a Cisco-LinkSys E900 router as my gateway + LAN router + WiFi Router. WiFi on the router is configured at "G" because I don't have any WiFi devices that can do anything higher than that. On the wired side, I have a PC and more recently a Raspberry Pi 2 connected using Cat 5e cables to ports 1 and 2 of the router. I do a speed test (speedtest.net, statically saved "preferred server" to ensure consistent results) twice a day to confirm I am getting what I am paying for.

ISP connection is a Static IP connection, with lease controllable if you set the router to DHCP IP mode. I tested it both ways, calling the ISP's tech support team to clear DHCP leases and sessions between tests.


The problem:
As of a week ago, I noticed miserable speeds in the range of 20-30 Mbps in my speedtests. Initially, thinking it was an ISP-side issue, I filed tickets. But the technician that came over used his laptop to directly connect (without going through my router) and I realized the router may be the bottleneck. I tested again using my systems (PC and a Laptop) that I was indeed able to get 90+ Mbps when not using the router.

I tried the WMM and QoS settings (enabling, disabling) with no effect. The router had the latest, but stock firmware. I also tried flashing it with DD-WRT firmware and tested again with no improvement in the results.

To workaround the question of if the router is the problem, I tried with two other routers: An old LinkSys WRT54G (that I originally used and upgraded from to the e900) and a new Asus RT N56U purchased off Amazon. Both those routers didn't fare any better and showed the same results.


Any ideas here before I throw away the router? :-(

 

[netwrks]

The WRT54G and LinkSys E900 only have 100mb WAN ports, which is going to slow you down. Meaning you are not going to see 100Mbps throughput on the WAN side. The router to connect to your ISP modem, would be the ASUS, as it has gig WAN and LAN ports. If the ASUS functions correctly, it should be a matter of correct router configuration and, or, FW upgrade.

 

[htismaqe]

It sounds like he tried the Asus and the problem remained.

 

[netwrks]

It sounds like he tried the Asus and the problem remained.

Yes, that is correct. He did. But, out of the 3 routers, the ASUS will be best suited for his internet connection, based on the device type - gig ports etc. That's why I implied of the device is healthy..

 

[Sujay Sarma]

Yes, that is correct. He did. But, out of the 3 routers, the ASUS will be best suited for his internet connection, based on the device type - gig ports etc. That's why I implied of the device is healthy..

Further investigation seems to reveal that the WAN port is somehow stuck at 10 Mbps Full Duplex.

@netwrks: Yes, I tried the ASUS. The WRT54G was simply an exercise to eliminate issues. I had used that router for years before needing to upgrade off it (I got both the new 100 Mbps connection and "N" wifi devices that the WRT54G could not support). I did not trust the config / results of the ASUS router at that point because it was fresh out of the box. However, all three gave the same disgusting speeds in the speedtest.

I have eliminated everything now and the results all seem to point to something being seriously wrong with using a router with the connection. Plan now is to go out in the morning (it is now midnight here) get myself an old-style Ethernet NIC and configure routing on my PC, downgrading the E900 from its gateway role.

PS: newbie Q: how long does it take around here for newbies to leave the "moderation required" status?

 

[thiggins]

PS: newbie Q: how long does it take around here for newbies to leave the "moderation required" status?

Not long. But your response that copied the OP's reply copied an anti-spam trigger word that held you up.

 

[netwrks]

Further investigation seems to reveal that the WAN port is somehow stuck at 10 Mbps Full Duplex.

@netwrks: Yes, I tried the ASUS. The WRT54G was simply an exercise to eliminate issues. I had used that router for years before needing to upgrade off it (I got both the new 100 Mbps connection and "N" wifi devices that the WRT54G could not support). I did not trust the config / results of the ASUS router at that point because it was fresh out of the box. However, all three gave the same disgusting speeds in the speedtest.

I have eliminated everything now and the results all seem to point to something being seriously wrong with using a router with the connection. Plan now is to go out in the morning (it is now midnight here) get myself an old-style Ethernet NIC and configure routing on my PC, downgrading the E900 from its gateway role.

PS: newbie Q: how long does it take around here for newbies to leave the "moderation required" status?

The router and modem may not be negotiating speeds correctly. You can also try installing an unmanaged gig switch between the router and modem to see if the port negotiation corrects itself. Have also seen a CAT5e cable not working correctly between a modem and router. You could try a CAT6 cable to see if the speed / negotiation be tween the devices sorts itself out.

 

[Sujay Sarma]

@netwrks Have tried those combos. The thing is, when ever the E900 becomes the gateway, it becomes < 30 Mbps (it hovers so much around the 20 Mbps mark that I am inclined to think its actually doing 10 Mbps Full Duplex).

Anyways, I have worked around the issue now and built my own router, the old style, using two NICs (TP-Link TG-3468) in a PC and a Gigabit switch (got the D-Link DGS-1008A) -- both models for no reason other than that the next-door retailer had them in plenty. My internal network is now happily humming away in Gigabit speed, with full N wifi using the same E900 and my internet connection at 100 Mbps Full Duplex.

Thanks folks!