Related Documentation
Using Loopback Testing for ATM Interfaces
- Checklist for Using Loopback Testing for ATM Interfaces
- Diagnosing a Suspected Hardware Problem with an ATM1 or ATM2 IQ Interface
- Creating a Loopback
- Setting Clocking to Internal
- Verifying That the ATM Interface Is Up
- Clearing ATM Interface Statistics
- Pinging the ATM Interface
- Checking for ATM Interface Error Statistics
- Diagnosing a Suspected Circuit Problem
Checklist for Using Loopback Testing for ATM Interfaces
Purpose
To use loopback testing for ATM interfaces.
Action
Table 1 provides links and commands for using loopback testing for ATM interfaces.
Table 1: Checklist for Using Loopback Testing for ATM Interfaces
Tasks | Command or Action |
|---|---|
| Diagnosing a Suspected Hardware Problem with an ATM1 or ATM2 IQ Interface | |
Connect the transmit port to the receive port. | |
[edit interfaces interface-name (sonet-options | t3-options)] | |
[edit interfaces interface-name] | |
show interfaces at-fpc/port/pic | |
clear interfaces statistics at-fpc/port/pic | |
ping interface at-fpc/port/pic local-IP-address bypass-routing count 1000 rapid | |
show interfaces at-fpc/port/pic extensive | |
| Diagnosing a Suspected Circuit Problem | |
[edit interfaces interface-name (sonet-options | t3-options)] | |
Perform Steps 2 through 6 from Diagnosing a Suspected Hardware Problem with an ATM1 or ATM2 IQ Interface. | |
Diagnosing a Suspected Hardware Problem with an ATM1 or ATM2 IQ Interface
Problem
When you suspect a hardware problem, perform the following steps to verify if there is a hardware problem.
Solution
To diagnose a suspected hardware problem with an ATM1 or ATM2 IQ interface, follow these steps:
- Creating a Loopback
- Setting Clocking to Internal
- Verifying That the ATM Interface Is Up
- Clearing ATM Interface Statistics
- Pinging the ATM Interface
- Checking for ATM Interface Error Statistics
Creating a Loopback
You can create a physical loopback or configure a local loopback to help diagnose a suspected hardware problem. Creating a physical loopback is recommended because it allows you to test and verify the transmit and receive ports.
If a field engineer is not available to create the physical loopback, you can configure a local loopback for the interface. The local loopback creates a loopback internally in the Physical Interface Card (PIC).
Creating a Physical Loopback
Create a physical loopback from the transmit port to the receive port.
 | Note: Make sure you use single-mode fiber for a single-mode port and multimode fiber for a multimode port for SONET media. |
- To create a physical loopback at the port, connect the transmit port to the receive port using a known good cable.
When you create and test a physical loopback, you are testing the transmit and receive ports of the PIC. This action is recommended if a field engineer is available to create the physical loop as it provides a more complete test of the PIC.
Configuring a Local Loopback
Purpose
Because ATM interfaces can be either SONET or T3, you use the sonet-options or t3-options statements to configure a local loopback. Figure 1 illustrates a local loopback configured for an ATM interface.
Figure 1: Local Loopback
Action
To configure a local loopback without physically connecting the transmit port to the receive port, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces interface-name (sonet-options | t3-options)
- Configure the loopback:[edit interfaces interface-name (sonet-options | t3-options)]user@host# set loopback local
- Verify the configuration:user@host# show
For example:
[edit interfaces (t3-1/0/0 t3-options)]user@host# show loopback local; - Commit the change:user@host# commit
For example:
[edit interfaces t3-1/0/0 t3-options]user@host# commit commit complete
Meaning
When you create a local loopback, you create an internal loop on the interface being tested. A local loopback loops the traffic internally on that PIC. A local loopback tests the interconnection of the PIC but does not test the transmit and receive ports.
| Note: Remember to delete the loopback statement after completing the test. |
Setting Clocking to Internal
Purpose
Clocking is set to internal because there is no external clock source in a loopback connection.
Action
To configure clocking to internal, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces interface-name
- Configure the clocking to internal:user@host# set clocking internal
- Verify the configuration:user@host# show
For example:
[edit interfaces t3-1/0/0]user@host# show clocking internal; - Commit the change:user@host# commit
For example:
[edit interfaces t3-1/0/0]user@host# commit commit complete
Meaning
The clock source for the interface is set to the internal Stratum 3 clock.
Verifying That the ATM Interface Is Up
Purpose
Displaying the status of the ATM interface provides the information you need to determine whether the physical link is up or down.
Action
To verify that the status of the ATM interface is up, use the following Junos OS CLI operational mode command:
Sample Output 1
The following sample output is for an OC3 ATM interface:
user@host> show interfaces at-2/0/0
Physical interface: at-2/0/0, Enabled, Physical link is Up
Interface index: 22, SNMP ifIndex: 42
Link-level type: ATM-PVC, MTU: 4482, Clocking: Internal, SONET mode, Speed: OC3 , Loopback: Local, Payload scrambler: Enabled
Device flags : Present Running
Link flags : None
Input rate : 0 bps (0 pps)
Output rate : 0 bps (0 pps)
SONET alarms : None
SONET defects : None
Logical interface at-2/0/0.0 (Index 29) (SNMP ifIndex 49)
Flags: Point-To-Point SNMP-Traps Encapsulation: ATM-SNAP
Input packets : 0
Output packets: 0
Protocol inet, MTU: 4470, Flags: None
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.1.0/30, Local: 192.168.1.1
VCI 1.100
Flags: Active
Total down time: 0 sec, Last down: Never
Traffic statistics:
Input packets: 0
Output packets: 0
Sample Output 2
The following sample output is for a T3 ATM interface:
user@host> show interfaces at-0/1/0 Physical interface: at-0/1/0, Enabled, Physical link is Up Interface index: 90, SNMP ifIndex: 18 Link-level type: ATM-PVC, MTU: 4482, Clocking: Internal, Speed: T3 , Loopback: None, Payload scrambler: Enabled, Mode: C/Bit parity, Line buildout: 10, ATM Encapsulation: PLCP Device flags : Present Running Link flags : None Current address: 00:90:69:0c:c0:1f Last flapped : 2002-08-14 16:25:07 UTC (00:00:42 ago) Input rate : 0 bps (0 pps) Output rate : 0 bps (0 pps) Active alarms : None Active defects : None
Sample Output 3
The following sample output is for an OC3 ATM interface:
user@host> show interfaces at-2/0/1
Physical interface: at-2/0/1, Enabled, Physical link is Down
Interface index: 23, SNMP ifIndex: 43
Link-level type: ATM-PVC, MTU: 4482, Clocking: Internal, SONET mode, Speed: OC3 , Loopback: None, Payload scrambler: Enabled
Device flags : Present Running Down
Link flags : None
Input rate : 0 bps (0 pps)
Output rate : 0 bps (0 pps)
SONET alarms : LOL, LOS
SONET defects : LOL, LOF, LOS, SEF, AIS-L, AIS-P, RDI-P, PLM-P
Logical interface at-2/0/1.10 (Index 30) (SNMP ifIndex 65)
Flags: Device-Down Point-To-Point SNMP-Traps Encapsulation: ATM-SNAP
Input packets : 0
Output packets: 0
Protocol inet, MTU: 4470, Flags: None
Addresses, Flags: Dest-route-down Is-Preferred Is-Primary
Destination: 192.168.100.0/30, Local: 192.168.100.1
VCI 2.100
Flags: Active
Total down time: 0 sec, Last down: Never
Traffic statistics:
Input packets: 0
Output packets: 0
Sample Output 4
The following sample output is for a T3 ATM interface:
user@host> show interfaces at-0/1/0 Physical interface: at-0/1/0, Enabled, Physical link is Down Interface index: 90, SNMP ifIndex: 18 Link-level type: ATM-PVC, MTU: 4482, Clocking: Internal, Speed: T3 , Loopback: None, Payload scrambler: Enabled, Mode: C/Bit parity, Line buildout: 10, ATM Encapsulation: PLCP Device flags : Present Running Down Link flags : None Current address: 00:90:69:0c:c0:1f Last flapped : 2002-08-09 11:36:15 UTC (5d 04:14 ago) Input rate : 0 bps (0 pps) Output rate : 0 bps (0 pps) Active alarms : PLL, LOF, LOS Active defects : PLL, LOF, LOS
Meaning
Sample output 1 shows that the physical link is up and there are no SONET alarms or defects.
Sample output 2 shows that the physical link is up and there are no active alarms or defects.
Sample output 3 shows that the physical link, the device flags, and interface flags are down, and that there are SONET alarms and defects. When you see that the physical link is down, there may be a problem with the port.
Sample output 4 shows that the physical link, the device flags, and interface flags are down, and that there are active alarms and defects. When you see that the physical link is down, there may be a problem with the port.
For more information about problem situations and actions to take for a physical link that is down, see Table 2.
Table 2: Problems and Solutions for a Physical Link That Is Down
Problem | Actions |
|---|---|
Cable mismatch | Verify that the cable connection is correct. |
Damaged fiber or coax cable or dirty fiber cable | Verify that the cable can successfully loop a known good port of the same type. |
Too much or too little optical attenuation (for an OC3 or OC12 ATM interface) | Verify that the attenuation is correct per the PIC optical specification. |
The transmit port is not transmitting within the dBm optical range per the specifications (for an OC3 or OC12 ATM interface) | Verify that the Tx power of the optics is within range of the PIC optical specification. |
Clearing ATM Interface Statistics
Purpose
You must reset ATM interface statistics before you initiate the ping test. Resetting the statistics provides a clean start so that previous input or output errors and packet statistics do not interfere with the current investigation.
Action
To clear all statistics for the interface, use the following Junos OS CLI operational mode command:
Sample Output
Meaning
This command clears the interface statistics counters for interface at-4/0/2 only.
Pinging the ATM Interface
Purpose
After you have put the port in a local loopback, run the ping test using the following Junos OS CLI operational mode command:
Action
Sample Output
user@host> ping interface at-2/0/0.0 192.168.1.1
bypass-routing count 1000 rapid PING 192.168.1.1 (192.168.1.1): 56 data bytes !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! --- 192.168.1.1 ping statistics --- 1000 packets transmitted, 1000 packets received, 0% packet loss round-trip min/avg/max/stddev = 0.423/0.740/26.822/0.829 ms
Meaning
This command sends 1000 ping packets out of the interface to the local IP address. The ping should complete successfully with no packet loss. If there is any persistent packet loss, open a case with the Juniper Networks Technical Assistance Center (JTAC) at support@juniper.net, or at 1-888-314-JTAC (within the United States) or 1-408-745-9500 (from outside the United States).
Checking for ATM Interface Error Statistics
Purpose
Persistent interface error statistics indicate that you need to open a case with JTAC.
Action
To check the local interface for error statistics, use the following Junos OS CLI operational mode command:
Sample Output
The following sample output is for an OC3 ATM interface:
user@host> show interfaces at-2/0/0 extensive
Physical interface: at-2/0/0, Enabled, Physical link is Up
Interface index: 22, SNMP ifIndex: 42, Generation: 21
Link-level type: ATM-PVC, MTU: 4482, Clocking: Internal, SONET mode, Speed: OC3 , Loopback: None, Payload scrambler: Enabled
Device flags : Present Running
Link flags : None
Hold-times : Up 0 ms, Down 0 ms
Statistics last cleared: 2002-07-29 14:28:14 EDT (00:00:26 ago)
Traffic statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
Input errors:
Errors: 0, Drops: 0, Invalid VCs: 0, Framing errors: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 0,
L2 mismatch timeouts: 0
Output errors:
Carrier transitions: 0, Errors: 0, Drops: 0, Aged packets: 0
SONET alarms : None
SONET defects : None
SONET PHY: Seconds Count State
PLL Lock 0 0 OK
PHY Light 0 0 OK
SONET section:
BIP-B1 0 0
SEF 0 0 OK
LOS 0 0 OK
LOF 0 0 OK
ES-S 0
SES-S 0
SEFS-S 0
SONET line:
BIP-B2 0 0
REI-L 0 0
RDI-L 0 0 OK
AIS-L 0 0 OK
BERR-SF 0 0 OK
BERR-SD 0 0 OK
ES-L 0
SES-L 0
UAS-L 0
ES-LFE 0
SES-LFE 0
UAS-LFE 0
SONET path:
BIP-B3 0 0
REI-P 0 0
LOP-P 0 0 OK
AIS-P 0 0 OK
RDI-P 0 0 OK
UNEQ-P 0 0 OK
PLM-P 0 0 OK
ES-P 0
SES-P 0
UAS-P 0
ES-PFE 0
SES-PFE 0
UAS-PFE 0
Received SONET overhead:
F1 : 0x00, J0 : 0x00, K1 : 0x00, K2 : 0x00
S1 : 0x00, C2 : 0x13, C2(cmp) : 0x13, F2 : 0x00
Z3 : 0x00, Z4 : 0x00, S1(cmp) : 0x00, V5 : 0x00
V5(cmp) : 0x00
Transmitted SONET overhead:
F1 : 0x00, J0 : 0x01, K1 : 0x00, K2 : 0x00
S1 : 0x00, C2 : 0x13, F2 : 0x00, Z3 : 0x00
Z4 : 0x00, V5 : 0x00
ATM status:
HCS state: Sync
LOC : OK
ATM Statistics:
Uncorrectable HCS errors: 0, Correctable HCS errors: 0, Tx cell FIFO overruns: 0, Rx cell FIFO overruns: 0,
Rx cell FIFO underruns: 0, Input cell count: 0, Output cell count: 8830024, Output idle cell count: 8830026,
Output VC queue drops: 0, Input no buffers: 0, Input length errors: 0, Input timeouts: 0, Input invalid VCs: 0,
Input bad CRCs: 0, Input OAM cell no buffers: 0
PFE configuration:
Destination slot: 2
CoS transmit queue Bandwidth Buffer Priority Limit
% bps % bytes
0 best-effort 0 0 0 0 low none
1 expedited-forwarding 0 0 0 0 low none
2 assured-forwarding 0 0 0 0 low none
3 network-control 0 0 0 0 low none
Logical interface at-2/0/0.0 (Index 29) (SNMP ifIndex 49) (Generation 28)
Flags: Point-To-Point SNMP-Traps Encapsulation: ATM-SNAP
Traffic statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Local statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Transit statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
Protocol inet, MTU: 4470, Flags: None, Generation: 31 Route table: 0
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.1.0/30, Local: 192.168.1.1, Broadcast: Unspecified, Generation: 59
VCI 1.100
Flags: Active
Total down time: 0 sec, Last down: Never
ATM per-VC transmit statistics:
Tail queue packet drops: 0
Traffic statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Sample Output
The following sample output is for a T3 ATM interface:
user@host> show interfaces at-0/1/0 extensive
Physical interface: at-0/1/0, Enabled, Physical link is Up
Interface index: 90, SNMP ifIndex: 18, Generation: 89
Link-level type: ATM-PVC, MTU: 4482, Clocking: Internal, Speed: T3 , Loopback: None, Payload scrambler: Enabled,
Mode: C/Bit parity, Line buildout: 10, ATM Encapsulation: PLCP
Device flags : Present Running
Link flags : None
Hold-times : Up 0 ms, Down 0 ms
Current address: 00:90:69:0c:c0:1f
Last flapped : 2002-08-14 16:25:07 UTC (00:00:21 ago)
Statistics last cleared: 2002-08-14 16:25:26 UTC (00:00:02 ago)
Traffic statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
Input errors:
Errors: 0, Drops: 0, Invalid VCs: 0, Framing errors: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 0,
L2 mismatch timeouts: 0
Output errors:
Carrier transitions: 0, Errors: 0, Drops: 0, Aged packets: 0
Active alarms : None
Active defects : None
DS3 media: Seconds Count State
PLL Lock 0 0 OK
Reframing 0 0 OK
AIS 0 0 OK
LOF 0 0 OK
LOS 0 0 OK
YELLOW 0 0 OK
EXZ 0 0
LCV 0 0
PCV 0 0
FERR 0 0
LES 0
PES 0
PSES 0
SEFS 0
UAS 0
PLCP defects: Seconds Count State
LOF 0 0
YELLOW 0 0
ATM defects: Seconds Count State
LCD 0 0
ATM status:
HCS state: Sync
LOC : OK
PLCP statistics (errored seconds):
Framing errors : 0(0)
Bit interleaved parity errors: 0(0)
Far end block errors : 0(0)
ATM Statistics:
Uncorrectable HCS errors: 0, Correctable HCS errors: 0, Tx cell FIFO overruns: 0, Rx cell FIFO overruns: 0,
Rx cell FIFO underruns: 0, Input cell count: 0, Output cell count: 96041, Output idle cell count: 96040,
Output VC queue drops: 0, Input no buffers: 0, Input length errors: 0, Input timeouts: 0, Input invalid VCs: 0,
Input bad CRCs: 0, Input OAM cell no buffers: 0
Packet Forwarding Engine configuration:
Destination slot: 0
CoS transmit queue Bandwidth Buffer Priority Limit
% bps % bytes
0 best-effort 95 42499200 95 0 low none
3 network-control 5 2236800 5 0 low none
Meaning
Check for any error statistics that may appear in the output. There should not be any input or output errors. If there are any persistent input or output errors, open a case with the JTAC at support@juniper.net, or at 1-888-314-JTAC (within the United States) or 1-408-745-9500 (from outside the United States).
Diagnosing a Suspected Circuit Problem
When you suspect a circuit problem, it is important to work with the transport-layer engineer to resolve the problem. The transport-layer engineer may ask you to create a loop from the router to the network, or the engineer may create a loop to the router from various points in the network.
To diagnose a suspected circuit problem, follow these steps:
- Creating a Loop from the Router to the Network
- Creating a Loop to the Router from Various Points in the Network
Creating a Loop from the Router to the Network
Purpose
Creating a loop from the router to the network allows the transport-layer engineer to test the router from various points in the network. This helps the engineer isolate where the problem might be located. Figure 2 illustrates a loop from a router to the network.
Figure 2: Loop from the Router to the Network
Action
To create a loop from the router to the network, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces interface-name (sonet-options | t3-options)
- Configure the remote loopback:[edit interfaces interface-name (sonet-options | t3-options)]user@host# set loopback remote
- Verify the configuration:user@host# show
For example:
[edit interfaces t3-1/0/0 t3-options]user@host# show loopback remote; - Commit the change:user@host# commit
For example:
[edit interfaces t3-1/0/0 t3-options]user@host# commit commit complete
Creating a Loop to the Router from Various Points in the Network
Purpose
The transport-layer engineer creates a loop to the router from various points in the network. You can then perform tests to verify the connection from the router to that loopback in the network.
Action
After the transport-layer engineer has created the loop to the router from the network, you must verify the connection from the router to the loopback in the network. Follow Steps 2 through 6 in Diagnosing a Suspected Hardware Problem with an ATM1 or ATM2 IQ Interface. Keep in mind that any problems encountered in the test indicate a problem with the connection from the router to the loopback in the network.
By performing tests to loopbacks at various points in the network, you can isolate the source of the problem.
