pwwn and nwwn

[prasadcm]

Hello - What is the difference between PWWN and NWWN? Do MDS's only recognize PWWN? If so, how do I know I got the right WWN in the zone?

[oerkan]

Hi,

PWWN is the port world wide name, whereas NWWN is the node world wide name.

In the SAN OS, Zone membership criteria is based on WWNs or FC IDs.

–Port world wide name (pWWN)—Specifies the pWWN of an N port attached to the switch as a member of the zone.

–Fabric pWWN—Specifies the WWN of the fabric port (switch port's WWN). This membership is also referred to as port-based zoning.

FC ID—Specifies the FC ID of an N port attached to the switch as a member of the zone.

–Interface and switch WWN (sWWN)—Specifies the interface of a switch identified by the sWWN. This membership is also referred to as interface-based zoning.

Interface and domain ID—Specifies the interface of a switch identified by the domain ID.

–Domain ID and port number—Specifies the domain ID of an MDS domain and additionally specifies a port belonging to a non-Cisco switch.

–IP address—Specifies the IP address (and optionally the subnet mask) of an attached device.

Thanks,

Hakan.

[jordankatzarov]

Prasad,

The difference is important in case of zoning.

Port World Wide Name(pWWN) is the logical number for the specific port in the MDS Switch. Every port has pWWN. Node WWN (nWWN), actually is the WWN of the device connected to the switch. In a specific zone you can define the members using both pWWN and nWWN. If pWWN is used, zoning remains independent for the device attached to the port. If the nWWN is used, that device remains constant for the specified zone.

Regards,

Dancho

[prasadcm]

Hello -

Thanks all for the info. So when I plug in my host, and my storage, to the MDS, and in the Fab Mgr I see couple of WWNs, do I need to be concerned whether they are PWWNs or NWWNs?

In other words, can I just go ahead and add what I see to a zone and expect it to work?

Prasad.

[groutley]

Hi,

I just wanted to clarify the terms here. And try to keep to an industry standard, and not invent more terms to create confusion.

WWNN is the industry standard term used as the Identifier for a Node, hence WorldWideNodeName.

WWPN is is the unique Identifier of the individual Port within a Node, hence WorldWidePortName.

pWWN is a new term from Cisco, which describes the Identifier of an individual port in the switch or director - portWorldWideName.

Now while each method of zoning has its own advantages and disadvantages, I would like to point out that if the switches pWWN's are used for zoning, that if your switch was to fail and require replacement, your zoning definitions are NOT transferable between switches, So on switch replacement a complete zoning recreate is required.

[dmcloon]

pWWN and WWPN are the same thing. A pWWN/WWPN can reside in either a switch, HBA or target. You may zone HBAs and targets using their pWWN.

nWWN and WWNN are the same thing. A nWWN/WWNN can reside in either a switch, HBA or target. We DO NOT provide zoning based on nWWN.

When talking about the nWWN of a switch we often call this the switch WWN (sWWN). Do a "show switch wwn" to see the base sWWN that shipped with your chassis. Starting from the base sWWN we allocate a unique sWWN in each VSAN. A "show fcdomain" will reveal the sWWN for each VSAN. The sWWN is used in things like principal switch selection, IVR, fabric binding (eg FICON), interface (fcx/y) based zoning, FCIP Special Frame, and calculating the port fWWNs. Note: If the chassis is changed the sWWN will change!

When talking about the pWWN of a switch interface, we in Cisco often refer to this as an fWWN. One of the zoning methods available is fWWN. An fWWN is a Fabric Port WWN. Just think of an fWWN as a pWWN on the switch side. As mentioned, the fWWN values are derived from the sWWN.

From the config guide, following forms of zoning are allowed:

– Port world wide name (pWWN). Specifies the pWWN of an N port attached to the switch as a member of the zone.

– Fabric pWWN. Specifies the WWN of the fabric port (switch port’s WWN). This membership is also referred to as port-based zoning.

– FC ID—Specifies the FC ID of an N port attached to the switch as a member of the zone.

– Interface and switch WWN (sWWN)—Specifies the interface of a switch identified by the sWWN. This membership is also referred to as interface-based zoning.

– Interface and domain ID—Specifies the interface of a switch identified by the domain ID.

– Domain ID and port number—Specifies the domain ID of an MDS domain and additionally specifies a port belonging to a non-Cisco switch.

– IP address—Specifies the IP address (and optionally the subnet mask) of an attached device.

Dallas

Sydney TAC

[Surya ARBY]

I need some help to get a better understanding;

In all the config examples I see; zoning is always done with port-WWN; never with node-WWN.

How does it work if the host uses multipathing; identifying a target through it's node-WWN ?

Do I have to enforce zoning with node-WWN in this case or does it still use port-WWN in the FC frames ?

[Kris Vandecruys]

Hi Surya,

Maybe this helps:  If you zone a host with 2 ports (and 1 nwwn, obviously) with some storage pwwn, using the nwwn of the host, your 2 host ports can talk to the storage, but also to each other. This is generally considered a Bad Thing.

HTH,

Kris

[Surya ARBY]

Thank you.

But in your example the two ports of the host will be connected to different fabrics, so no communication possible between them; am I right ?

Can you correct me if I'm wrong (I come from the LAN world) :

When designing a SAN; if you have n host and 1 storrage array; you will setup n zones (one for each host); each zone with two members : the WWpN of the storage array and the WWpN of the current host; and then you repeat the same thing over the second fabric. So you have full isolation between hosts; each host can only see the storrage array. To me zoning is better if you enable only point-to-point communications ?

Also what's going on with the physical layer ? I've always believed that all entites always used WWpN in the FC frames; as I see only WWpN when I issue a "show flogi database" for example.

I still don't really understand how FC handles multipathing with WWnN from a pure networking point of view (physical layer).