How does setting a static IP on a mobile device prevent linux router from assigning that IP address?

technically true, but the term 'static ip' has a specific meaning.

what is handed out by a dhcp server can't be a static ip, even if it never changes.

the term 'static ip' has a specific meaning, and it's not handed out by a dhcp server. the address may be the same one every time the dhcp lease is renewed, but that doesn't make it a static ip.

yes, because whatever ip address he picks, it will almost certainly conflict with something on another network.

which means changing it every time he leaves/returns.

a very bad choice.

eventually, he did, and the reason is valid.

it's the proposed solution that's bad.

they do exist and it's not that rare.

then you haven't seen very many routers.

if the router supports dhcp server, and just about every router does, then it's very easy to use dns rather than ip addresses.

it also doesn't need to be done in the router at all. use zeroconf, which is entirely independent of the router.

Do you mean it'll hand out a previously-assigned address to a different computer, or that it hands out the same IP address to a the same device after the router is rebooted?

If the former, yeah, that's a problem due to the leases file being wiped out. More an artifact of non-persistent storage than anything - typically, I've only seen this kind of behavior in cheap SOHO routers though.

If the latter, that's how DHCP is supposed to work. Both sides keep a record of how long the lease lasts for. The DHCP server's record includes the client's MAC address; and as long as the client requests the IP be refreshed before the expiration date/time, the client will receive the same IP address.

Typically the client refreshes the IP at the lease half-life (for example, every 12 hours on a 24-hour DHCP Lease).

In , Whiskers suggested:

The reason for the many access points is both for coverage and for convenience.

Coverage is so that I can beam to the farthest reaches of the house, and to the barn, and to the pool, and to the treehouse out back, etc.

Convenience is simply because I'm on WISP so I happen to have lots of powerful radios on hand that dwarf (in ERP transmit power and receiver sensitivity) that of a typical SOHO router.

Here is a picture of just a couple of those spare radios in the game room.

The range of these "wireless extenders" can be measured in miles, but only if there are no walls or trees or homes or mountains in the way.

Some of my access points are set up on the same SSID while others use different SSIDs, mostly dictated by the inability of the iOS equipment to easily report the BSSID (the Android, Linux, and Windows equipment doesn't have that limitation).

The extension router is also a spare router, set up as a bridge, as I recall, wired to the main router (because the specific version of the spare WRT54G doesn't allow wireless repeaters).

In summary, the network is set up for coverage and convenience.

My radios are all capable of something like ten or fifteen kilometers (assuming similar equipment & protocols on the other end), since they're all spare radios from a professional WISP setup.

Where I live (Santa Cruz Mountains), there is no cable and no DSL. There is just the wide open ether.

So we're all adept at getting our Internet from APs that are miles away.

While satellite is always possible, we're all on WISP, so most of us are very familiar with the various antennas and radios necessary.

Over time, we've upgraded our radios from low power (just a few miles) to higher power (up to the legal limit) for both 2.4GHz and now, 5GHz (for noise reasons), so, fundamentally, we all have radios to spare out here.

To put all those spare radios to good use, we often attach them to our routers as free "range extenders", where the extended range can be measured in miles if we so desire.

In fact, when some houses have network problems (e.g., when the antenna blows down), we have been known to set up tripods where we beam our Internet access to the neighbor (with our small WISP's permission) from house to house where we have successfully transmitted our signal for more than a mile.

Since we live in mountains, this is easy, as long as the Fresnel zone is relatively clear.

Thanks for that advice on the factory reset!

It was a great thing when the manufacturers started putting the reset button in the POE which saves us having to climb a tree or clamber on the roof just to factory reset our radios!

Why? He only needs to set the static IP for his home network, not for any others. Once set, each network will be recognised automatically by his phone and use the settings created specifically for it (which in most cases will be to accept DHCP).

A sensible choice, incompletely implemented.

except when it doesn't.

horrible choice.

the solution is simple: dns and let the router handle ip management, which is what it's designed to do. alternately, reserved dhcp.

He doesn't have to change anything. Just move and continue using the phone normally.

Your wrong opinion noted.

The setting is done only on the router, not the APs.

On the phone, you have to do the setting for all your home SSIDs. In that case, it is easier to assign an IP on the router instead than on the phone. A single point of configuration.

You have a device that allows settings for one access point to influence the settings for any or all other access points? It's faulty.

I agree that the router should allocate the unchanging IP number the user wants it to allocate. There is no reason not to set that same IP number on the device as well, in its settings for that network. Relying on the router accepting a static IP number offered by the device, without setting the router to match, could lead to problems eventually if the user's luck runs out.

All the home routers I have used have DHCP capabilities, none have configurable DNS capabilities.

which doesn't always work.

I get names such as "android-c2653....", and ping from the computer does not work.

He did right on the first post.

Your opinion noted.

The fixed IP setting applies only to a single SSID. Does not affect other networks. When he goes out, the phone will connect to a different SSID and use the configuration for that different SSID, which is "auto", ie, "DHCP".

And even in that case of same SSID by chance, it would have a different password.

Right.