WWN vs FCID

[kwftide1]

I understand WWNs are 64 bits and FCIDs are 24 bits and I understand the fabric assigns FCIDs when a device logs into the fabric (FLOGI).

Here's what seems confusing:

Since a device is communicating via FC and that protocol uses FCIDs, what is the purpose of a WWN? If devices (disregarding HP-UX and AIX) point to WWNs but the fabric uses FCIDs, where is this mapping stored on the server and how does it work exactly? Is there a table like a ARP cache? If so, when does it time out?

My point is, there is no field in the FCID frame for WWNs - only source and destination FCIDs. So, how do WWNs play into this picture?

[tblancha]

You can think of WWN's as MAC addresses and FCID as the layer3 IP address. So, the WWN is burned into the HBA firmware. HPUX and AIX take the FCID of the storage they are talking to and enter it into a persistent file on the /etc filesystem. The wwn to FCID mapping can be seen with show flogi database and show fcns database.

[mrfrase]

Also, the part of the operation of the HBA on the host is to store and retain a Login map of all targets, it stores both FCID's and PWWN's of devices on the SAN so it can build frames for commands that are sent to storage devices, FC devices learn PWWN of target port from PLOGI ACC , the 24 bit FCID is used to route frame through the SAN using FSPF, 24 bit lookup is much faster then 64 bit lookup, but remember access control to storage is many times controlled by PWWN, both for zoning on Switch and also the controller port on the array. This PWWN is checked at PLOGI for access control.

[kwftide1]

So, if the initiator HBA learns the target's FCID during PLOGI, how long is the FCID retained by the server? Is the FCID retained until a logout occurs or does it time out (like an arp entry)?

One reason I ask is I'd like to fully understand the ramifications of changing FCIDs.

[jejoseph]

Host learns target's fcid thro' Plogi into NameServer,if it is zoned together. It is retained

as long as storage is in the fabric with same fcid

and host has PLOGIed onto the storage.

FCID of storage is retained in the host until

LOGO (explicit).

If the storage is not in fabric, then RSCN

is generated and host requeries the name server

for the storage, if it is not there, then

HBA cleans up resources related to that FCID.

[kwftide1]

Thanks for all the replies!

[m-abooali]

H,

I am also having this confusion. I have a different post going on a Nexsus 9148 IOS upgrade. I am so new to this data center and VSAn work and configuring nexus. my back ground has always been routing and switching but I have been assign this task without having formal training or experience on this. I have been reading the whole day so far and getting closer however, i still need to know where i start on a nexus. For example: on this singe Nexus 9148 that will be used for two zones:

I have:

A	xxxxx2vio1_ZoneA	xxxxx2vio1	xxxxx2vio1_p1	10:00:00:00:c9:8c:8e:24
A	xxxxxx2vio1_ZoneA	xxxxx2vio1	svs9san05_a2	20:24:00:80:e5:18:9e:56

B	xxxxxx3vio1_ZoneB	xxxxxx3vio1	svs9san05_a1	20:14:00:80:e5:18:9e:56
B	xxxxxxx3vio1_ZoneB	xxxxxxx3vio1	svs9san05_b1	20:15:00:80:e5:18:9e:56

vmhost-xxxxxx02_ZoneA

vmhost-xxxxxx

svs9san05_a2

20:24:00:80:e5:18:9e:56

vmhost-xxxxxx02_ZoneB	vmhost-xxxxxx	svs9san05_a1	20:14:00:80:e5:18:9e:56
vmhost-xxxxxxx02_ZoneB	vmhost-xxxxxx-02	svs9san05_b1	20:15:00:80:e5:18:9e:56
vmhost-xxxxxxx02_ZoneB	vmhost-xxxxxx-02	vmhost-xxxxxx02_p2	21:00:00:24:ff:29:e2:6b

I have edited the above table showing samples of each zone (about 6 lies of A and 6 lines of B with WWN numbers shown). so, what are those 28-bits numbers? are they defined as is or they are defined in the Switch? I have been told to use these same numbers.

so, any help to get me going will be appreciated. I have been reading on pwwn numbers and other variables/definitions/standards but I still do not know where to begin except for:

Command

Explanation

switch#conf t

Enters configuration terminal

switch(config)# zoneset name

Zoneset_10 vsan 10

Enters Zoneset configuration mode. Creates Zoneset_10 for vsan 10 if it

does not exist

switch(config-zoneset)# zone

name Host_A-Target_1

Enters in-line Zone configuration mode. Creates zone Host_A-Target_1 in

vsan 10 and as a member to Zoneset_10 if it does not exist

switch(config-zoneset-zone)#

member pwwn

21:01:00:e0:8b:39:a9:07

Add pwwn as a member of zone Host_A-Target_1

switch(config-zoneset-zone)#

member pwwn

21:00:00:20:37:af:a5:93

Add pwwn as a member of zone Host_A-Target_1

switch(config-zoneset-zone)#

zone commit vsan 10

Commits the changes made to the zones and zoneset in vsan 10. Used only

if enhanced zoning is enabled

switch(config)# zoneset activate

name Zoneset_10 vsan 10

Sets the active zoneset as the currently configured Zoneset_10 in vsan 10.

Note that only 1 zoneset can be active in a vsan at a time

switch(config)# zone commit

vsan 10

Commits the change made to the zoneset in vsan 10. This step is required

in enhanced zoning mode after an activation in order for the new activation

to occur

So, you think I may be able to pull this off using what is listed above and other commands sets that i have in document that I am going to use as my guide? Cisco document. i may be asking for to much but I do not have any other choice but to reach out.

single Cisco Nexus 9148 and two zones.

Best Regards,

Masood