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WNDR3700v4 in AP mode speed degradation over WAN port

GGill
Aspirant

WNDR3700v4 in AP mode speed degradation over WAN port

WNDR3700v4 firmware V1.0.2.78

 

I have the Netgear router set to AP mode, with static IP address, and default gateway set to my Zhone router which faces the outside world. (The Zhone is an ISP-supplied router over which I have little configuration control.)

  • On the LAN side of the Netgear I have a desktop with gigabit ethernet card, connected by cable to the Netgear.
  • The WAN side of the Netgear is connected to a LAN port on the Zhone router.
  • I have a gigabit-ethernet laptop connected to another LAN port on the Zhone router.

To measure speed of the connection between the desktop and laptop, I ran iperf -s (server mode) on the laptop and iperf -c (client mode) on the desktop. The TCP speed was reported as around 3Mbits/s - very slow. With iperf -c -R on the desktop (which reverses the test direction, laptop server is sender instead of desktop client), the TCP speed was about 200Mbits/s.

 

I then rebooted the Netgear. The iperf reported TCP speed (with -R and without) increased to about 650Mbits/s.

 

If instead of connecting the WAN port on the Netgear to the Zhone, I connect a LAN port on the Netgear to the Zhone (using the same cable), the desktop and laptop communicate at around 950Mbits/s, close to the maximum theoretical speed of 1Gbit/s. (The Netgear is still in AP mode, though I guess that shouldn't make a difference if not using the Netgear's WAN port.) Similarly, if I skip the Netgear entirely, connecting the desktop directly to a LAN port on the Zhone, I get around 950Mbits/s speed to the laptop.

 

When in AP mode many config options in the Netgear are inaccessible, so it's hard for me to tell if there's a setting interfering with communication over the WAN port. Also the asymmetrical speeds before the router reboot (3Mbits/s from desktop to laptop, 200Mbits/s from laptop to desktop), and the fact that the reboot fixed that, but still didn't achieve full speed (650Mbits/s), make me suspicious about what is happening on the WAN port side.

 

The workaround clearly is to ignore the WAN port on the Netgear and use a LAN port to connect to the Zhone, but

  • I put the Netgear where it is specifically because I have 4 devices I want to connect to LAN ports, and Netgear's AP mode let me use the WAN port to connect to the rest of the network; and
  • I'm still curious to know why there would be a performance problem across the WAN port, if there might be a configuration reason and not just failing hardware. (The Netgear router has been my workhorse for a few years until moving to a new place.)

 

 

Model: WNDR3700v4|N600 Wireless Dual Band Gigabit Router
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Accepted Solutions
ElaineM
NETGEAR Employee Retired

Re: WNDR3700v4 in AP mode speed degradation over WAN port

AP Mode disables hardware acceleration, so the CPU needs to handle packets going between the LAN and WAN ports. The Broadcom chip can handle switching between LAN ports without CPU involvement.

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GGill
Aspirant

Re: WNDR3700v4 in AP mode speed degradation over WAN port

I did search before posting but didn't find this topic until it was suggested after posting:

It suggests that WAN port use in AP mode is significantly worse because of extra packet processing. I wonder why that's true - what keeps the WAN port from just being another switched LAN port like the others, when in AP mode?

Message 2 of 3
ElaineM
NETGEAR Employee Retired

Re: WNDR3700v4 in AP mode speed degradation over WAN port

AP Mode disables hardware acceleration, so the CPU needs to handle packets going between the LAN and WAN ports. The Broadcom chip can handle switching between LAN ports without CPU involvement.

Message 3 of 3
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