I am trying to disable auto-negotiation on the WAN port of my Asus RT-AC66U router. This is because it has problems with the CAT5 cable which is embedded inside the wall of my apartment. The issue is that on boot, sometimes it recognizes 1000BaseT, and sometimes 100BaseT speed, and I have a 300Mbit contract. This cable is cross wired (from provider switch to my router), and right now it cannot be replaced. I have tried with Tomato and Merlin firmware, and I don't have this option to modify. Should I buy a cheap/used Cisco router? I only need 1 Wan and max 5 LAN outputs. And what would you recommend.

  • Nothing will fix the miswired cable other than fixing the miswired cable. – David Schwartz Nov 1 '16 at 9:39
  • Wire is not miswired - or isn't it supposed to be crossed? I am just speculating that only the wire must be the problem for this. As the router still gets 1000BaseT, I thought I could force it to be always this speed. – ChefLeBoef Nov 1 '16 at 9:43
  • Add another crossed cable to the link to uncross it ... – DavidPostill Nov 1 '16 at 11:19
  • I will try this, as from what I remember the cable from socket to WAN is straight. But for my knowledge - what will the behaviour be if, for example, I have a Cisco router which has auto-sensing disabled on WAN and speed set to 1000BaseT? – ChefLeBoef Nov 1 '16 at 12:49
  • @ChefLeBoef If you have a router with auto-sensing disabled but set to 1000BaseT, it won't work with anything else because other devices won't use 1000BaseT unless they negotiate it. You need straight through cables, you need the correct pairs-to-pins mapping, and you need autonegotiation. Do not force anything, fix things. If they're broken, trying to force them to work will fail horribly. – David Schwartz Nov 1 '16 at 20:02

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