Cisco 3750 Redundancy Test

The Cisco 3750 Catalyst Series offer high class switching functionality such as StackWise support with a 32 Gbit dual ring (16+16G). This means that you have a 32 Gigabit throughtput between Stack Switches.

During some testing with 2 stacked switches, I was able to simulate a failure by issuing the command:

reload slot 2 -> This will reload the module 2 switch.

switch# reload ?
LINE Reason for reload
at Reload at a specific time/date
cancel Cancel pending reload
in Reload after a time interval
slot Slot number card
standby-cpu Standby RP


Switch# sh switch det
Switch/Stack Mac Address : 0021.XXXX.XXXX
H/W Current
Switch# Role Mac Address Priority Version State
----------------------------------------------------------
*1 Master 0021.XXXX.XXXX 15 1 Ready
2 Member 0022.XXXX.XXXX 1 1 Ready



Stack Port Status Neighbors
Switch# Port 1 Port 2 Port 1 Port 2
--------------------------------------------------------
1 Down Down None None
2 Ok Ok 1 1

Unable to send a l2trace request to

How to detect and diagnose cabling problems using Time Domain Reflector (TDR) in Cisco devices

Goal: diagnose and resolve cabling problems
What it does: The device sends a signal through the cable and compares the reflected signal to the initial signal sent.

Important:
- Only works with 10/100/1000 copper
- SFP and copper 10/100 not supported

- Run it with the IOS Command:
test cable-diagnostics tdr interface <..>
show cable-diagnostics tdr interface

TDR will detect these cabling problems:
- Open, broken, or cut twisted-pair wires. The wires are not connected to the wires from the remote device.
- Shorted twisted-pair wires. The wires are touching each other or the wires from the remote device.

Example:
SWITCH# test cable-diagnostics tdr interface GigabitEthernet 1/0/47
TDR test started on interface Gi1/0/47
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

SWITCH#show cable-diagnostics tdr interface GigabitEthernet 1/0/47
TDR test last run on: March 04 19:37:15

Interface Speed Local pair Pair length Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/47 1000M Pair A 0 +/- 10 meters Pair B Normal
Pair B 0 +/- 10 meters Pair A Normal
Pair C 0 +/- 10 meters Pair D Normal
Pair D 0 +/- 10 meters Pair C Normal


The PRBS test can only be executed for TenG interfaces:
SWITCH# test cable-diagnostics prbs start interface TenGigabitEthernet ?
<1-9> TenGigabitEthernet interface number

line protocol is down (err-disabled)

SWITCH#sh int G0/18
GigabitEthernet0/18 is down, line protocol is down (err-disabled)
Hardware is Gigabit Ethernet, address is 001f.7777.7777 (bia 7777.7777.7777)
Description SWITCH-A
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255255, txload 1255, rxload 1255
Encapsulation ARPA, loopback not set
Keepalive not set
Auto-duplex, Auto-speed, link type is auto, media type is unknown
input flow-control is off, output flow-control is unsupported
ARP type ARPA, ARP Timeout 040000
Last input never, output never, output hang never
Last clearing of show interface counters never
Input queue 07500 (sizemaxdropsflushes); Total output drops 0
Queueing strategy fifo
Output queue 040 (sizemax)
5 minute input rate 0 bitssec, 0 packetssec
5 minute output rate 0 bitssec, 0 packetssec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 3 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out


Produced logs:
%LINK-5-CHANGED: Interface GigabitEthernet0/18, changed state to administratively down
%GBIC_SECURITY_CRYPT-4-VN_DATA_CRC_ERROR: GBIC in port Gi0/18 has bad crc
%PM-4-ERR_DISABLE: gbic-invalid error detected on Gi0/18, putting Gi0/18 in err-disable state
%LINK-3-UPDOWN: Interface GigabitEthernet0/18, changed state to down



This could be associated with a problem in SFP.
Check if the SFP is correctly connected, and if it is a Cisco SFP!