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Topic: OpenWRT + TP Link + VLAN tagging Wan interface slow

The content of this topic has been archived on 31 Mar 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

Last week I've tested serveral TP Link routers (WDR 3600/4200 & Archer C7 v2) with openWrt ( 14.07 / 15.05 )
on my  500/500Mbit Fiber connection (PPPoE).

But the maximum speed I get is 270Mbit
http://i.imgur.com/wak3R18.png

Is there a issue with vlan tagging on the Wan interface? Without a vlan tag the lan/wan speed are very good (+/- 900Mbit)

(Last edited by sappien on 29 May 2015, 11:26)

Could be a MTU issue, the VLAN tagging may be increasing the frame sizes above the MTU of one or more interfaces, forcing packets to be fragmented with a corresponding performance hit.

I would check all the MTUs on your test path for starters. Try reducing the MTU on the test machines either side of the router a bit, say -50, and see if performance improves.

I'm no expert on how this should work, all I know that is that I once had a router that turned into a blackhole when I connected it to a VLAN switch. After much head-scratching, I found that reducing the MTUs on the interfaces of the connected PCs to 1468 suddenly allowed traffic to pass. MTU of 1469 made it a blackhole again.

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