Hi,

Ans 1: DWDM is a networking technology to combine multiple optical carrier signals into one signal. A typical SAN switch will connect to a port of a DWDM switch. The network of switches between the SAN switches in 2 sites are transparent. It seems as a simple connection. So, as far as I know, there is no command to detect it.

Ans 2: Both Cisco and Brocade support DWDM. We previously used Brocade 48K and 32B2. Now we have migrated to Cisco M9k.

I can't answer the last question. The gurus can help you here.

#3 - when someone says "core" switch, it's really what they consider a core switch in their environment, topology of their fabric. Someone could have a 9148 as their core switch and then have a bunch of small 9124 as edge switches. Then other shops could have 5 x 9710 as their core with a bunch of 9513 as edges.  You can have an edge switch that is the principal switches, it does not have to be the core switch.

9513a1# show fcdomain domain-list vsan 114

Number of domains: 2
Domain ID              WWN
---------    -----------------------
  0x06(6)    20:72:00:0d:ec:f0:17:01 [Local] [Principal]
 0x10(16)    20:72:00:0d:ec:c9:07:81

One thing to add to dynamox's great answer above is while it's allowed to basically any switch in a fabric be the principal switch, it is considered a best practice to have your "most powerful" switch be the principal. In this case, "most powerful" is not in terms of port count but rather in terms of "switch compute" power. So, it usually works out best to use a later generation switch.

Thank you all for the answers.

So regarding the DWDM is there no way to findout its existence unless customer tells about it.

As per Ashfaq, if a port in a switch will be connected to a port of a DWDM switch, will the WWN of the DWDM switch willnot show in the non-DWDM switch ?

you will not see an flogi on the port that is connected to DWDM gear. Also typically ports that connect to DWDM gear are long range SFP something that you could look for as an indication of some kind of extended distance connectivity, IE

9513a1# sh int fc 1/24 br

-------------------------------------------------------------------------------
Interface  Vsan   Admin  Admin   Status          SFP    Oper  Oper   Port
                  Mode   Trunk                          Mode  Speed  Channel
                         Mode                                 (Gbps)
-------------------------------------------------------------------------------
fc1/24     1      auto   on      trunking         lwcr   TE      4    80

9513a1# sh flogi database interface fc1/24
No flogi sessions found.

Notice "long wave laser and "single mode"

9513a1# sh int fc 1/24 transceiver 
fc1/24 sfp is present 
    Name is CISCO-JDSU      
    Manufacturer's part number is JSHR42L305102   
    Revision is 0000
    Serial number is JUT104401R9     
    Cisco part number is 
    Cisco pid is 
    FC Transmitter type is long wave laser cost reduced
    FC Transmitter supports long distance link length
    Transmission medium is single mode (SM) laser
    Supported speeds are - Min speed: 1000 Mb/s, Max speed: 4000 Mb/s
    Nominal bit rate is 4300 Mb/s
    Link length supported for 9/125mm fiber is 10.100 km
    Cisco extended id is unknown (0x0)

    No tx fault, no rx loss, in sync state, diagnostic monitoring type is 0x68
    SFP Diagnostics Information:
        Temperature           :  38.17 C    
        Voltage               :   3.30 V       
        Current               :  19.55 mA         
        Optical Tx Power      :  -3.96 dBm        
        Optical Rx Power      :  -9.05 dBm        
        Tx Fault count  : 0
    Note: ++  high-alarm; +  high-warning; --  low-alarm; -low-warning