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Static vs. Dynamic IP Address

What is an IP address? 

An Internet Protocol address (IP address) is an identifier assigned to a device that is connected to a network. There are two versions of IP addresses that are used: a 32-bit format (IP version 4) and a 64-bit format (IP version 6). IPv4’s format is xxx.xxx.xxx.xxx. IPv6’s format is xx:xx:xx:xx:xx:xx:xx:xx. The IPv6 was developed because the pool of IPv4 addresses is being depleted. 

Static vs. dynamic IP address 

A static IP address never changes. A dynamic IP address is assigned to the device once it is connected and changes over time. 

Most users do not need a static IP address. A static IP is needed when external devices need to remember the IP address. Virtual private networks (VPNs) and other remote access solutions need to remember your IP address, so they require the device to use a trusted IP address. VPNs are used for security purposes.  

Dynamic IP addresses and DHCP leases 

Since dynamic IP addresses change over time, the network must know what IP address to assign the device. DHCP stands for “Dynamic Host Configuration Protocol.” The DHCP server manages the pool of IP addresses that will be used to assign to network devices. The IP addresses are assigned for a limited time then changed. 

The time period that the address is valid is called a “lease duration.” When it expires, the client must stop using this address. If the rule is not followed, there is a chance that another client will be assigned the same IP address, which will cause a conflict with IP frames trying to deliver to the right device. 

DHCP lease duration is expressed in seconds. A lease can be labelled as “infinite” for devices that do not need to change their IP address, such as printers and application servers.  

There are times when a host (client) needs to continue using the same IP address for a longer time than what the lease timer is set to. The host (client) then contacts the DHCP server asking it to extend the lease. If the DHCP server does not reply, the client attempts to rebind the lease via a broadcast to any DHCP server on the network. If there is no answer, the host (client) must then restart the whole process from the beginning.  

During the lease period, the host (client) can also ask for lease termination. This is done in order to free up the IP address so that it can be used by another host (client) on the network. This is normally performed when the host (client) shuts down or disconnects from the network. 

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