HP StorageWorks Fabric OS 5.3.x administrator guide (5697-0244, November 2009)

Fabric OS 5.3.0 administrator guide 367
Troubleshooting trunking problems
If you have difficulty with trunking, try the solutions in this section.
Listing link characteristics
If a link that is part of an ISL Trunk fails, use the trunkDebug command to troubleshoot the problem,
as shown in the following procedure:
1. Connect to the switch and log in as admin.
2. Enter the following command:
The trunkDebug command displays the possible reason that two ports cannot be trunked, including the
following reasons:
• The switch does not support trunking.
• A trunking license is required.
• Trunking is not supported in switch interoperability mode.
• Port trunking is disabled.
• The port is not an E_Port.
• The port is not 2 Gbit/sec or 4 Gbit/sec.
• The port connects to different switches.
• The ports are not same speed, or they are not set to a valid speed.
• The ports are not set to the same long distance mode.
• Local or remote ports are not in same port group.
• The difference in the cable length among trunked links is greater than the allowed difference.
This example shows that port 3 is not configured as an E_Port:
Recognizing buffer underallocation
For SAN Switch 2/8V, SAN Switch 2/16V, SAN Switch 2/32 and SAN Director 2/128 models, if there is
an underallocation or overcommitment of buffers to ports configured for extended trunking, the switches at
both ends of the trunk try to disable some ports so that others can operate using the available buffers.
(Standard trunks are not affected by buffer allocation.)
This issue of buffer underallocation does not apply to the SAN Switch 4/32, SAN Switch 4/32B and
4/256 SAN Director models.
A port disabled at one end because of buffer underallocation causes all the disabled ports at the other
end to become enabled. Some of these enabled ports become disabled due to a lack of buffers, which in
turn triggers ports to be enabled once again at the other end. While the system is stabilizing the buffer
allocation, it warns that ports are disabled due to lack of buffers, but it does not send a message to the
console when buffers are enabled. The system requires a few passes to stabilize the buffer allocation.
Ultimately, the number of ports for which buffers are available come up and stabilize. You should wait for
stabilization, and then proceed with correcting the buffer allocation situation.
To get out of buffer-limited mode on E_ports or LD_ports:
1. Change the LD/L1/L2/L0.5 port speed to a lower speed (of non-buffer limited ports).
2. Change the LD port’s estimated distance to a shorter distance (of non-buffer limited ports).
trunkDebug port , port
port Specifies the number of a port in an ISL Trunking group.
switch:admin> trunkdebug 3 5
port 3 is not E port
switch:admin>