07-18-2011 03:56 AM
a G-Port is a port that has finished link initialization (up to word synchronization) and is now waiting to become either F-Port or E-Port.
If a G-Port receives a FLOGI frame, this means an end-device is attached to it, so it will attempt to initialize as F-Port.
If a G-Port receives an ELP (exchange link parameters) frame, this means another switch is attached to it, so it will attempt to initialize as E-Port.
If a port stays in G-Port status for extended period of time, means it cannot transition to neither F-Port nor E-Port, and this is an unusual situation. Means that connected device is not able to talk with switch port properly.
One common reason for this nowadays is incorrect Fill Word configuration on an 8G link. Could as well be software misconfiguration or even firmware bug.
Hope this helps,
07-18-2011 05:34 AM
The one I'm experiencing now is G port in blade center interconnects due to interoperatibility with Cisco SAN's. This is has been fixed in higher versions of Cisco NXOS but we are yet to upgrade.
There are N number of reasons for a G port, you will have to be specific about your problem if you need help in resolution.