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Comment by TazeTSchnitzel | Hacker News Reader

No. It should prompt you to renew it, but not just do it, since IP address conflicts probably mean one end is badly configured.

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It doesn't presently prompt to renew — it just says that there's a conflict and doesn't tell you which settings panel might be helpful. Only a very tiny subset of users will actually try to reconfigure their router or make other such changes as the result of this information. Options requiring a prompt before automatic renewal would be great for those users, but it's not relevant in 99%+ of cases.

No, they're relevant in far more than <1% of csses. Forgotten DHCP renewal is not the only reason that IP address conflicts happen.

But that doesn't mean that alongside the warning the computer can't try to get a new IP address by itself, even if it won't fix the problem 100% of the time.

No. If something is wrong with the current network config, don't automatically muck around with it so that I can't troubleshoot the problem myself. It's important to understand the current state to figure out how you got into that broken state; kind of like a breakpoint at the first exception. Automatically renewing is like 'On Error Goto Next'.

That said, I agree that it should suggest renewing the DHCP lease.

Well if the current network config is set to simply use DHCP, then renewing DHCP is a pretty safe move.

If the DHCP is set to serve a static IP for the MAC, the problem will presist, if the DHCP server is dynamic it will just do what its desgined to do and assign a unused address fixing the problem while not changing the network configuration at all.

For good product usability, being proactive, and getting 80% of the use cases right is much more important than being making no mistake and shift the decision (and blame) to the user. Especially since most of the time the user has no technical background to make the correct decisions. I used to think like you until I read The Inmates are running the Assylum[0]. I still do for my personal workflow (that is why I prefer archlinux to ubuntu), but I try to be proactive in the error catching in the software I write.

[0]: http://www.amazon.com/The-Inmates-Are-Running-Asylum/dp/0672...

Yes, and that end is your Mac. It did this on purpose, and it should just renew.

[ http://news.ycombinator.com/item?id=2755461 ]

The usual cause of this for most people is that they've rebooted their router and it kept the leases in memory, so it isn't aware it assigned the IP to multiple computers. Really, automatically renewing the lease if you're on DHCP is probably the best behaviour for a home/simple OS. For computers on a network administered by professionals, it should be possible to disable this (and other automatic) behaviour.

Does anyone know what the iPhone/iPad/etc. do in this case?

The iDevices all bounce around getting multiple addresses within the DHCP range. Last time I was administrating an office network full of iDevices I had to increase the DHCP range to account for the iDevice's bouncing all over the range and using up addresses pretty needlessly.

Most sane DHCP servers will also attempt to ping an IP address before offering it (and won't offer it, of course, if it gets a response).

ping and ARP ... ping can be turned off for instance.

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