Technical data

12-10 Fabric OS Administrator’s Guide
Publication Number: 53-0000518-09
Troubleshooting Trunking Problems
12
• 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 SilkWorm 3250, 3850, 3900, 12000, and 24000 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 SilkWorm 4100 and SilkWorm 48000 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).
3. Change LD/L1/L2/L0.5 back to L0 (of non-buffer limited ports).
4. If you are in buffer-limited mode on the LD port, then increase the estimated distance.
These changes are implemented only after disabling (portDisable) and enabling (portEnable) the buffer-
limited port (or buffer-limited switch).
Reconfiguring a port to LD from another mode can result in the port being disabled for lack of buffers–
this does not apply to the SilkWorm 4100 and SilkWorm 48000 (using FC4-16 and FC4-32 port blades).
If this happens:
• In Fabric OS v4.2.x, reconfigure the disabled LD port back to the original mode.
switch:admin> trunkdebug 3 5
port 3 is not E port
switch:admin>