Tuesday, August 23, 2011

Time Domain Reflectometer (TDR)

Time Domain Reflectometer allows network administrators to remotely identify the location of cable breaks and faults. The TDR test sends a signal along a cable, measures the time it takes for the echo to return, and computes the distance to the break using the built-in intelligent DSPs of the port interfaces.

TDR is an online test that displays the connected wire pairs of the port and the distances to their breaks (if present) upon the completion of the test.

TDR test is supported on most Cisco Catalyst series switches.
Below shows the execution of the commands on a Catalyst 6500 WS-X6748-GE-TX switch port interface:
C6500#test cable-diagnostics tdr int gi1/1
TDR test started on interface Gi1/1
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

C6500#
C6500#sh cable-diagnostics tdr int gi1/1


TDR test last run on: August 23 10:48:23
Interface Speed Pair Cable length        Distance to fault   Channel Pair status
--------- ----- ---- ------------------- ------------------- ------- ------------
Gi1/1     1000  1-2  0    +/- 6  m       N/A                 Pair B  Terminated

                3-6  0    +/- 6  m       N/A                 Pair A  Terminated

                4-5  0    +/- 6  m       N/A                 Pair D  Terminated

                7-8  0    +/- 6  m       N/A                 Pair C  Terminated


C6500#

Detailed command output capture:
C6500#sh ver
Cisco IOS Software, s72033_rp Software (s72033_rp-ADVENTERPRISE_WAN-M), Version 12.2(33)SXJ, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2011 by Cisco Systems, Inc.
Compiled Thu 17-Mar-11 15:10 by prod_rel_team

ROM: System Bootstrap, Version 12.2(17r)S4, RELEASE SOFTWARE (fc1)

 C6500 uptime is 1 hour, 37 minutes
Uptime for this control processor is 1 hour, 37 minutes
Time since C6500 switched to active is 1 hour, 36 minutes
System returned to ROM by reload at 07:23:18 UTC Tue Jun 21 2011 (SP by reload)
System image file is "disk0:s72033-adventerprise_wan-mz.122-33.SXJ.bin"
Last reload reason: Unknown reason


cisco WS-C6509-E (R7000) processor (revision 1.4) with 458720K/65536K bytes of memory.
Processor board ID SMC1237001T
SR71000 CPU at 600Mhz, Implementation 0x504, Rev 1.2, 512KB L2 Cache
Last reset from s/w reset
1 Virtual Ethernet interface
48 FastEthernet interfaces
146 Gigabit Ethernet interfaces
1917K bytes of non-volatile configuration memory.
8192K bytes of packet buffer memory.

65536K bytes of Flash internal SIMM (Sector size 512K).
Configuration register is 0x2102

C6500#
C6500#sh int gi1/1
GigabitEthernet1/1 is up, line protocol is up (connected)
  Hardware is C6k 1000Mb 802.3, address is 0023.5d23.f000 (bia 0023.5d23.f000)
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 10/100/1000BaseT
  input flow-control is off, output flow-control is on
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:03, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  L2 Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 0 pkt, 0 bytes mcast: 0 pkt, 0 bytes
     11 packets input, 1632 bytes, 0 no buffer
     Received 3 broadcasts (0 IP 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
     3 packets output, 1770 bytes, 0 underruns
     0 output errors, 0 collisions, 1 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
C6500#
C6500#sh int gi1/1 capabilities
GigabitEthernet1/1
  Model:                 WS-X6748-GE-TX
  Type:                  10/100/1000BaseT
  Speed:                 10,100,1000,auto
  Duplex:                half,full
  Trunk encap. type:     802.1Q,ISL
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: percentage(0-100)
  Flowcontrol:           rx-(off,on,desired),tx-(off,on,desired)
  Membership:            static
  Fast Start:            yes
  QOS scheduling:        rx-(1q8t), tx-(1p3q8t)
  QOS queueing mode:     rx-(cos), tx-(cos)
  CoS rewrite:           yes
  ToS rewrite:           yes
  Inline power:          no
  Inline power policing: no
  SPAN:                  source/destination
  UDLD                   yes
  Link Debounce:         yes
  Link Debounce Time:    no
  Ports-in-ASIC (Sub-port ASIC) : 1-24 (1-12)
  Remote switch uplink:  no
  Dot1x:                 yes
  Port-Security:         yes
C6500#
C6500#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
C6500(config)#logging event link-status default
C6500(config)#end
C6500#
C6500#test ?
  aaa                AAA Authentication, Authorization and Accounting
  accelerated-cef    Test accelerated cef (Gemini)
  appletalk          APPLETALK diagnostic code
  autoshut           Autoshut test command
  beep               BEEP agents
  cable-diagnostics  Cable Diagnostics on Interface
  cef                Cisco Express Forwarding test command
  checkpoint         Checkpoint Facility test commands
  cisp               Test CISP protocol
  cwoir              CWAN OIR test commands
  diagnostic         Diagnostic commands
  dsp                Test DSP functions
  em                 Event Manager Test
  epm                EPM CTS test
  fallback           Fallback test
  fm                 Test FM
  glbp               Gateway Load Balancing Protocol test commands
  heartbeat          Heartbeat test commands
  hw-module          Test hardware module commands
  icc                ICC test commands
  iccshim            ICCSHIM test commands
  ifs                IFS TEST code
  interfaces         Network interfaces
  ip                 IP test commands
  iphc               IPHC testing
  ipmobile           IP Mobility Test commands
  l3-mgr             Test l3 mgr API
  lacp               Link Aggregation Control Protocol
  lbl-sync           Line by Line command sync info
  lcc                linecard configuration commands
  mcm                MDR Card Manager
  monitor            monitor test commands
  mpls               MPLS test commands
  oer                Test Optimized Edge Routing (OER)
  oir                OIR test commands
  pasvc              PPP over ATM SVC Test Driver
  platform           Test platform information
  pm                 Port Manager test commands
  rpc                RPC test commands
  sasl               Test SASL code.
  scp                SCP test commands
  snmp               snmp set test command
  ssm                SSM test commands
  sw-vlan            Test VLAN Manager feature
  track              Object Tracking test commands
  tunnel             Test tunnel
  upgrade            Test FPD image upgrade features
  vines              VINES diagnostic code
  wism               WiFi Services Module
  xdr                Test XDR communication

C6500#test cable-diagnostics ?
  tdr  test TDR on interface

C6500#test cable-diagnostics tdr ?
  interface  Specify an interface for TDR test
  module     Run TDR test on all the ports for the module

C6500#test cable-diagnostics tdr int gi1/1
TDR test started on interface Gi1/1
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

C6500#
10:48:23.983: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/1, changed state to down
10:48:23.995: %LINK-3-UPDOWN: Interface GigabitEthernet1/1, changed state to down
10:48:23.991: %LINEPROTO-SP-5-UPDOWN: Line protocol on Interface GigabitEthernet1/1, changed state to down
10:48:23.999: %LINK-SP-3-UPDOWN: Interface GigabitEthernet1/1, changed state to down
10:48:27.327: %LINK-3-UPDOWN: Interface GigabitEthernet1/1, changed state to up
10:48:27.331: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/1, changed state to up
10:48:27.335: %LINK-SP-3-UPDOWN: Interface GigabitEthernet1/1, changed state to up
10:48:27.339: %LINEPROTO-SP-5-UPDOWN: Line protocol on Interface GigabitEthernet1/1, changed state to up
C6500#
C6500#sh cable-diagnostics tdr int gi1/1


TDR test last run on: August 23 10:48:23
Interface Speed Pair Cable length        Distance to fault   Channel Pair status
--------- ----- ---- ------------------- ------------------- ------- ------------
Gi1/1     1000  1-2  0    +/- 6  m       N/A                 Pair B  Terminated

                3-6  0    +/- 6  m       N/A                 Pair A  Terminated

                4-5  0    +/- 6  m       N/A                 Pair D  Terminated

                7-8  0    +/- 6  m       N/A                 Pair C  Terminated


C6500#

Below lists the TDR usage guidelines:
= TDR can test cables for connectivity problems for up to a maximum length of 115 meters.
= Link state will be affected during TDR test.
= Do not start the test at the same time on both ends of the cable. Starting the test at both ends of the cable at the same time can results in misleading results.
= Do not change the port configuration during the TDR test, as this may result in misleading results.
= The interface must be enabled (no shutdown) before performing the TDR test.
C3750#test cable-diagnostics tdr int gi1/0/1
% Interface Gi1/0/1 is administratively down
% Use 'no shutdown' to enable interface before TDR test start.
C3750#
= If the port speed is 1000Mbps / 1Gbps and the link is up, do not disable the auto-MDIX feature.
= For fixed 10/100Mbps ports, disable the auto-MDIX feature on both sides of the cable before performing the TDR test. Failure to do so can result in misleading results.
= For all other conditions, the auto-MDIX feature must be disabled on both ends of the cable. Failure to disable auto-MDIX will interfere with the TDR test and results in misleading results.
= If the link partner has auto-MDIX enabled, it will interfere with the TDR test and results in misleading results. The workaround is to disable auto-MDIX on the link partner.

Below shows the execution of the commands on a Catalyst 3750 switch port interface:
SW2#sh run int fa1/0/1
Building configuration...

Current configuration : 49 bytes
!
interface FastEthernet1/0/1
 no mdix auto
end

SW2#
================================================================================
SW1#sh cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
                  D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
SW2              Gig 1/0/1         146              S I   WS-C3750- Fas 1/0/1
SW1#
SW1#sh run int gi1/0/1
Building configuration...

Current configuration : 52 bytes
!
interface GigabitEthernet1/0/1
 no mdix auto
end

SW1#
SW1#sh int gi1/0/1
GigabitEthernet1/0/1 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0022.552d.f481 (bia 0022.552d.f481)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:08, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     117 packets input, 17514 bytes, 0 no buffer
     Received 103 broadcasts (103 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 103 multicast, 0 pause input
     0 input packets with dribble condition detected
     43 packets output, 10677 bytes, 0 underruns
     0 output errors, 0 collisions, 2 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
SW1#
SW1#test cable-diagnostics tdr int gi1/0/1
Link state may be affected during TDR test
TDR test started on interface Gi1/0/1
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.
SW1#
SW100:23:47.078: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to down
SW100:23:48.084: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to down
SW100:23:51.868: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up
SW100:23:52.874: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to up
SW1#
SW1#sh cable-diagnostics tdr int gi1/0/1
TDR test last run on: March 01 00:23:46

Interface Speed Local pair Pair length        Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/1   100M  Pair A     N/A                Pair B      Normal
                Pair B     N/A                Pair A      Normal
                Pair C     1    +/- 2  meters Pair D      Short
                Pair D     1    +/- 2  meters Pair C      Short
SW1#

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