12-19-2005 09:10 AM - edited 03-03-2019 01:10 AM
Hi,
I've noticed that my Cat 3750 on the show buffers command is getting as many misses as hits:
Interface buffer pools:
supervisor_cpuq_15_pool buffers, 2040 bytes (total 4, permanent 4):
0 in free list (0 min, 4 max allowed)
6860407 hits, 6860403 misses
I assume this isn't normal and can it be adjusted?
I have an 8 channel Mux plugged into the switch passing data(IP) to a Router. Using a BERT tester I get errors after a few minutes. Eliminate the Cat 3750 and do the test again and I get no errors on the BERT.
Any ideas are appreciated.
Thanks
Wayne
12-19-2005 12:24 PM
The "misses" counts is misleading in Cat 3750
platform. There are 16 CPU queues in h/w and each
queue is allocated a fixed number of buffers. If the
fixed h/w allocation is used up, the IOS will try to
back fill from a software buffer pool. The "missed"
count in "show buffers" command is incremented each
time when a packet is received and there is no
buffer in the corresponding software pool. So
increasing misses does not necessarily mean packets
are dropped - it only means that the software buffer
pool is empty either because no software buffers
are allocated for the CPU queue, or all software
buffers are allocated inorder to back fill the
hardware buffers. Packets will be dropped only if
all hardware buffers used up. To determine whether
any CPU bound packets are dropped, you should use
the following 3750 platform command instead of the
generic "show buffers" IOS command.
"show platform port-asic stats drop"
12-20-2005 02:09 AM
Many thanks for your reply. Now I understand the output.
Rgds,
Wayne
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