Back To My Basics | WWN, WWNN and WWPN

        I've been posting blogs on various features and troubleshooting tips over the past few years. But I think it is time to go back to my basics. Something which I feel as the building block of a good system admin. In this 'Back To My Basics' series, I'll be revisiting some of the system basics.

You may be an administrator in VMware, Windows, Linux or even network. Do you think that you always get to hear something only from your area of expertise ? definitely not...The basics should be strong enough for you to understand technologies in the course of design or engineering discussions.

WWN

We all know about MAC address, it doesn't need any special introduction. MAC is an unique identifier of a Network Adapter. Network is one of the communication channel of the server. For attaching storage, we may use the same network if the storage is iSCSI based. If the traffic uses FC, we may need something called as an HBA (Host Bus Adapter) card in our server. HBA card is similar to a NIC, but only understands FC protocol.

WWN (World Wide Name) is a generic term which refers to a unique identifier of a FC device. FC device can be a HBA card or a SAN switch. If you are wondering what is a SAN switch, it is similar to an ethernet Switch, but connects FC devices as end nodes.

WWN are of two types:

World Wide Node Name - WWNN
World Wide Port Name   - WWPN

There will be only one WWNN for an FC device but there can be multiple WWPN !!! The number of WWPN depends on the number of ports in the FC device. If there are 'n' number of ports there will be 'n' WWPN for the device.

For eg: in a dual port HBA card, there will be 1 WWNN and 2 WWPN. For a fabric switch with 48 ports there will be 1 WWNN and 48 WWPN.

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