Hi,
do you use a fiber connection between the Extreme and Cisco switches? If so, activating UDLD on the Cisco is problematic, because it is a Cisco proprietary feature that does not work with other vendors' switches.
Using Ethernet flow control (active on the Cisco) is not a good idea in general, it might cause intermittent problems, like dropping one ping packet or the other.
The "keepalive 30" setting on the Cisco is dubious as well, as this should enable a Cisco proprietary keepalive mechanism, but the EXOS switch does not send responses.
Since you have configured BPDU Guard on the Cisco, you must not enable STP on the EXOS switch. You can check if BPDU Guard error disabled an interface using "show interfaces err-disable."
Thanks,
Erik