Ethernet shield hangs entire HTTP LAN


I've been running my arduino-based home automation system for the last couple of weeks perfectly well, but all of a sudden, whenever the official ethernet shield is plugged in, it effectively kills the entire LAN!

Browsers take ages to load the page, then once the page looks ok, they still think there's more to come so stay in the loading state. It spends ages resolving the host, generally.

What's weird is things like Skype are unaffected.

I've tried the simple webserver ethernet example to check it's not my code that's causing it, still with no joy.

Does anyone have any suggestions of what may be wrong?

I've had a look with WireShark and there's nothing obviously going to/from the arduino.

Thanks v much, Ed

I've had a look with WireShark and there's nothing obviously going to/from the arduino.

A switched LAN isolates traffic, so you'll need to be on the same ethernet segment with your sniffer - either by using a hub, or by mirroring traffic if it's a managed switch.


Very true! Back to watching the flashing LED not flash - it's strange, the RX/TX LEDs aren't flashing like crazy, so I can't imagine it's overloading the network, just doing something weird :S

Your DHCP system hasn't given another machine the same IP address as the Arduino ?. Some home routers are completely dumb when it comes to issuing IP addresses.

By chance it hasn't, but I will put the arduino's address outside the DHCP range to ensure it can't ever happen (once I've stopped it killing the network!!)


Hi, an is something everybody should have in his toolbox ;)

Always handy when there are problems with address resotuion on the network. Disconnect your computer from the router, disable DHCP and give it a static address for the test. Connect your computer to the arduino-ethernet shield, and you should be able to talk/debug (to) it without the router getting into the way.


Thanks for that - the problem with doing that is I won't know if it's killing the rest of the network! I guess it would let me see if it's sending out lots of packets, although I assume if it was sending out packets, the LEDs would be flashing.

Very, very strange :(