Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual page 124

Registers and Counters
S e n d d o c u m e n t c o m m e n t s t o n e x u s 5 k - d o c f e e d b a c k @ c i s c o . c o m .
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
Understanding Fibre Channel interface counters
The show interface command is very useful when troubleshooting physical layer or performance issues
with a Fibre Channel interface.
In the output of the command, observe the input/output counters and any input/output discards or errors.
When input discards increment, the FC packet does not have a valid route in the Forwarding Information
Base (FIB). All packets not having a route are considered discards and sent to the supervisor. These
packets are NOT dropped; however, they are policed before being sent to the supervisor. You should also
check the MAC ASIC for errors.
When output discards increment, packets are timing out in egress because the egress is too slow. Check
the attached device because it may be a slow draining receiver that is not responding, or not replenishing
buffer credits. This causes back pressure to occur on the Nexus 5000 FC interface.
Example:
switch# show interface fc2/1
fc2/1 is trunking
[snip]
Cisco Nexus 5000 Series Troubleshooting Guide
5-52
InLayer3Routed = 0
InLayer3RoutedOctets = 0
OutLayer3Routed = 0
OutLayer3RoutedOctets = 0
OutLayer3Unicast = 0
OutLayer3UnicastOctets = 0
OutLayer3Multicast = 0
OutLayer3MulticastOctets = 0
InLayer3Unicast = 0
InLayer3UnicastOctets = 0
InLayer3Multicast = 0
InLayer3MulticastOctets = 0
InLayer3AverageOctets = 0
InLayer3AveragePackets = 0
OutLayer3AverageOctets = 0
OutLayer3AveragePackets = 0
Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
Port WWN is 20:41:00:0d:ec:a4:02:80
1 minute input rate 5048 bits/sec, 631 bytes/sec, 9 frames/sec
1 minute output rate 6752 bits/sec, 844 bytes/sec, 9 frames/sec
36398816 frames input, 2422447564 bytes
0 discards, 0 errors
0 CRC, 0 unknown class
0 too long, 0 too short
36368010 frames output, 3213593392 bytes
0 discards, 0 errors
1 input OLS, 1 LRR, 0 NOS, 0 loop inits
1 output OLS, 2 LRR, 0 NOS, 0 loop inits
16 receive B2B credit remaining
250 transmit B2B credit remaining
0 low priority transmit B2B credit remaining
Interface last changed at Thu Jan 28 18:26:30 2010
cos7OutLost = 0
RxPause = 0
TxPause = 2266
Resets = 0
SQETest = 0
Chapter 5 Troubleshooting SAN Switching Issues
OL-25300-01