What is FLOGI PLOGI and PRLI In SAN Switch

What is FLOGI PLOGI and PRLI In SAN Switch? This blog has a detail explanation of three device login processes on the SAN switch. Basically, there are three device login process FLOGI, PLOGI and PRLI.


What is Device Login In SAN Switch?

Device Login is a series of processes that happen when a new node or device is connected to a Fabric. Once Device Login Process Completes then a device can communicate with other devices in the same fabric. Its Involves three steps FLOGI PLOGI and PRLI.

Components of Device Login In SAN Switch

Host – These are the server which is connected to Switch.
Array – These are the storage Array connected to Switch.
SAN Switch – A SAN switch that has FC Ports.

A device login process happens for all devices that connect to a Fabric for the first time.

What is FLOGI In SAN Switch
What is Device Login Process In SAN Switch

What is FLOGI Process in SAN Switch?

During the FLOGI process, a device sends its first frame to the SAN switch. The SAN switch assigns an FCID to the device and the end device confirms to the switch that it received an FCID. The switch uses this FCID to identify the end device connected to it in the SAN network.

FLOGI Process happens when a new device connects to SAN switch or fabric for the first time. The new devices send it the first frame to switch that contains information like WWPN and buffer to buffer credits (B2B credits).

What is PLOGI SAN Switch?

PLOGI Process has two steps, port initialization and registration in Name Server. During port initialization a host and switch exchange information like port type and port speed. SAN switch uses these information and negotiates with host.

During negotiation SAN switch will come to know whether the end device is a server or a storage by referencing the port type.

What is Name Server In SAN Switch?

During Name Server registration of PLOGI process the device register its information in the name server. This provides information to device about all other device which are registered in name server that it can communicate to.

Each fabric in the SAN switch network maintains a name server. This name server contains the information of every device connected to the SAN Fabric. Two devices in the SAN switch network can communicate only if both of them are in the name server.

What is Process Login (PRLI) In SAN Switch?

PRLI also stands for process Login. During this process, actual communication happens between two devices in SAN network. In simple terms, we can say that during PRLI, N_port communicates with another N_Port. In broad term a host communicates with storage array.

During the PRLI process, a host sends a PRLI request to a storage array. If proper SAN zoning and LUN masking exist then storage array accept the PRLI request and starts the communication between them.

Video Tutorial On Device Login Process SAN Switch

Watch the below video tutorial from YouTube explaining the device login process in SAN switch. Subscribe the channel for more such videos.

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