You have to check a few things before ISL'ing.  Change the INTEROP mode on the Brocade switch to 1. Also, make sure the Domain ID on the Brocade is 97+. If you McData switch's Domain ID is 1 then set the Brocade switch Domain ID to 98.  In addition verify that the following parameter settings match between the two switches:  BB Credits (16) EDTOV (2000) RATOV (10000) Data Field Size (2112)  Once you verify the above connect the ISL between the two switches. If your port is set to AUTO it should be set to E once the ISL connection is established.
I need to ISL the two switches in the subject. Does anyone have experience with these two switches and ISL? Any suggestions would be greatly appreciated!!!
Need to create an ISL between DS-5300B and Connectrix DS24-M2