The complaint I get most often goes like this: "the handheld is slow, and it keeps dropping out." I used to go straight to the access points, change the channel, and hope the problem went away. Sometimes it did. A week later it was back.
After it happened a few times, the pattern showed itself. The devices that dropped out were always the same ones, at the same time of day, while picking was at its busiest. That is not what a weak signal looks like. That is what two devices sharing one IP address looks like.
Why the clash happens
Some of the handhelds were given static IPs, because at some point somebody needed their addresses to stay put. The trouble is that those addresses sit inside the range DHCP still hands out. As long as the static device is switched on first, nothing happens. The moment it goes off, its address is leased to something else, and when it comes back on, both devices believe the address is theirs.
The symptom is never "cannot connect". What you get instead is a connection that comes and goes, pings that land one moment and vanish the next, and an application that fails to send data halfway through a job.
What I do now
I reversed the order of the checks:
- Start with the ARP table on the MikroTik, looking for an IP address that appears with two different MAC addresses.
- Match those MAC addresses against the device records. It is usually one handheld and one other device that nobody remembered to register.
- Move the static address out of the DHCP range, or switch the device to DHCP with a static lease on the router.
The third step is the one that helps most. With a static lease the address stays the same, but the router holds the list, rather than a manual record scattered across several people's memories.
A note to myself
When the complaint is "it keeps dropping out" rather than "it cannot connect", I stop guessing at the signal. An address clash is far more common, and proving it takes nothing more than one table on the router. The time left over can go to whatever actually needs fixing.