Cryptocurrency miners must have an IP address. Depending on your operation, they're either statically or dynamically assigned.
With a static IP, the miner's address is fixed; regardless of what happens at site, the miner will always request the exact same IP address. The greatest benefit this has to offer is in the event of an outage or loss of power to networking equipment, the miner will immediately return to the IP address it was originally using.
With DHCP, the router dynamically selects an available IP address and allocates it to the miner. For some configurable amount of time (the "lease time"), the miner will always receive the same address. In the event of an outage, the lease will expire and when power is restored or the miner is returned, it will possibly get a new one.
Why This Matters
Foreman needs to the know the IP address of the miner so it can obtain statistics and dispatch commands (ex: reboot, change pools, etc).
With static IPs, things won't fall out of sync (the miner's address in Foreman will always match the actual miner's address). With DHCP, things can shuffle, and this causes a disconnect between Foreman and the miner, resulting in the common 'Miner not updating' diagnosis.
How to Address This
If you're open to a static IP deployment, you can use Foreman to mass reconfigure your miners from DHCP to static IPs via a Bulk Edit Action. You'll upload a CSV that contains each miner's new configuration.
Given that static IPs introduce operational overhead, farms typically elect to leverage dynamic assignment. To help keep things aligned, Foreman provides 'Recurring Resyncs', a process where our system will automatically walk preconfigured subnets you define, locate miners by their MAC addresses, and automatically update their IP addresses to match the ones that were assigned by the router.
What this means? If you've configured resyncs correctly, when things periodically shuffle, you don't have to do a thing.
You'll know a miner is missing when you see a miner's IP in Foreman automatically reset to 0.0.0.0. This happens when we detect that the MAC address associated with a miner has changed, implying that network devices have shuffled. Another sign is a miner transitioning to 'Miner not updating' despite you knowing that the device is functioning properly.
Creating Recurring Resyncs
To find miners automatically and align their IP addresses, Foreman needs to know what to find and where to look. From the Pickaxe page, select 'Find Miners':
Specify the manufacturer, a 'Scan Type' of 'Re-Sync Miners (Recurring)', and a subnet range to crawl. The following shows searching for Antminers from 10.0.0.1 - 10.0.5.255:
You'll need to have a rough idea of how your network is structured so Foreman knows where to look. Additionally, you'll need to create multiple resyncs for overlapping IP ranges if there are multiple miner manufacturers that need to be located. The following example demonstrates locating Antminers, Avalons, and Whatsminers across similar subnets:
As you expand your network or add new miners, these ranges will need to be kept up-to-date.
It's recommended that a single resync be responsible for searching no more than 4,000 IP address. If your network covers more than 4,000 IP address, the resyncs should be split to scan different ranges (ex: one from 10.0.0.1 - 10.0.15.255, another from 10.0.16.1 - 10.0.30.255). This will let them run in parallel, reducing the total search time.
You'll need to create resyncs on every Pickaxe on the account, each responsible for evaluating the subnet ranges they typically monitor. As an example, assume a 16 container deployment across two Pickaxes, each responsible for 8 containers. Each Pickaxe would scan their separate, unique subnets and resyncs would be structured so they don't overlap. Otherwise, this would cause miners to move between agents.
You'll know things are working properly if you periodically see scans running when miners go offline. They'll appear top-right in the command status window as a Targeted Scan (scanning subnets, but looking for specific MAC addresses):
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