The miner cannot obtain the IP caused by the long DHCP lease

Trouble phenomenon:

Why does the long DHCP lease period cause the miner to fail to obtain the IP?

This phenomenon is common when the machine is replaced. When a large number of machines are replaced in an IP segment, the scanning software cannot scan these updated machines. However, the machine that has not been replaced can still work normally, the computer can also access the Internet normally, and it is useless to restore the factory settings. The IP segment does not exceed 250 machines, and the newly installed machines can operate normally on other network segments.

Cause Analysis:

1. Understand how the miner obtains the IP address:

Each miner comes with a MAC address when it leaves the factory. By default, the miner connects to the network to obtain an IP address through DHCP so that there will be a table of correspondence between the MAC address and the IP address of the mining machine in the router MAC address.

2. Understand what the address lease period is:

The address lease term refers to the validity period of the binding relationship between the MAC address and the IP address. For example, if the address lease period is 2 days and a mining machine is taken off the shelf, it will take another 48 hours for the binding relationship between the IP address and the MAC address to be Release; new miners can use the IP address.

Generally speaking, there are about 253 available addresses for a Class C network segment, which means that the MAC address and IP address correspondence table in the router can store up to 253. This number can be configured on the router's DHCP configuration interface.

If there are 250 machines in this network segment, 100 machines will be removed from the shelves, and 100 machines will be put on the shelves. Unfortunately, the binding relationship between the IP and MAC addresses of the 100 machines removed from the shelves has not been released, and the newly added 100 machines will not be able to obtain IP Addresses.

3. Fault judgment:

The miner cannot be scanned, and the miner cannot obtain an IP address. It may be because there is a problem with allocating the IP address of the network segment.

Troubleshooting ideas:

1. Check whether the router's DHCP service is enabled.

2. Check whether the number of addresses in the IP segment exceeds the number of existing machines in the router.

3. In the computer network sharing center-local connection-detailed information, check the IP lease time in the IP address. The IP address in the picture needs to expire at 1 o'clock on August 1st, which means this IP address needs to be used after this time.

4. If the time is obviously very long, the IP segment needs to be calculated, whether the number of machines that have not been removed from the shelves + the number of machines that have been removed + the number of new shelves exceeds the number of addresses in the IP segment. If it exceeds, the router needs to be restarted.

Result analysis:

The main reason for this situation is that the IP addresses occupied by the machines that have been removed from the shelves cannot be released in the DHCP server. These IPs cannot be released until the lease expires. As a result, the newly listed machines cannot obtain IP addresses. After restarting the router, DHCP will clear all the previous records, and the IP addresses of the machines that have been removed can be released.

Suggestions for later improvement:

1. Set the DHCP lease period to 2 hours to reduce the time occupied by the IP address.

2. When configuring the number of IP addresses in a single IP segment, try to be far larger than the actual number of machines to increase the operating space.