Use Loopback Testing for Multichannel DS3 Interfaces
- Checklist for Using Loopback Testing for Multichannel DS3 Interfaces
- Diagnose a Suspected Hardware Problem with a Multichannel DS3 Interface
- Create a Loopback
- Verify That the Interface Is Up
- Clear Interface Statistics
- Force the Link Layer to Stay Up
- Verify the Status of the Logical Interface
- Ping the Channelized Interface
- Check for Interface Error Statistics
- Diagnose a Suspected Circuit Problem
- Create a Loop from the Router to the Network
- Create a Loop to the Router from Various Points in the Network
Checklist for Using Loopback Testing for Multichannel DS3 Interfaces
Purpose
To use loopback testing to isolate Multichannel DS3 interface problems.
Action
Table 1 provides links and commands for using loopback testing for Multichannel DS3 interfaces.
Table 1: Checklist for Using Loopback Testing for Multichannel DS3 Interfaces
Tasks | Command or Action |
|---|---|
| Diagnose a Suspected Hardware Problem with a Multichannel DS3 Interface | |
Connect the TX port to the RX port. | |
[edit interfaces interface name
(t3-options | t1-options)] | |
show interfaces (ds-fpc/pic/port:channel:channel | t1-fpc/pic/port:channel) | |
clear interfaces statistics (t1-fpc/pic/port:channel | ds-fpc/pic/port:channel:channel) | |
[edit interfaces interface-name] | |
[edit interfaces interface-name] | |
show interfaces (ds- fpc/pic/port:channel:channel | t1-fpc/pic/port:channel) | |
ping interface (ds-fpc/pic/port:channel:channel | t1-fpc/pic/port:channel) local-IP-address bypass-routing count 1000 rapid | |
show interfaces (ds-fpc/pic/port:channel:channel | t1-fpc/pic/port:channel) extensive | |
| Diagnose a Suspected Circuit Problem | |
[edit interfaces interface-name
t3-options] | |
[edit interfaces interface-name t1-options] | |
Perform Steps 2 through 8 from Diagnose a Suspected Hardware Problem with a Multichannel DS3 Interface. | |
Diagnose a Suspected Hardware Problem with a Multichannel DS3 Interface
Problem
To diagnose a suspected hardware problem with a Multichannel DS3 interface, follow these steps:
Solution
- Create a Loopback
- Verify That the Interface Is Up
- Clear Interface Statistics
- Force the Link Layer to Stay Up
- Verify the Status of the Logical Interface
- Ping the Channelized Interface
- Check for Interface Error Statistics
Create a Loopback
Purpose
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 Multichannel DS3 port. 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).
Create a Physical Loopback
Action
To create a physical loopback at the port, connect the transmit port to the receive port.
Meaning
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.
Configure a Local Loopback
Action
To configure a local loopback, follow these steps:
- In configuration mode, go to the following hierarchy level,
depending on whether you are configuring a full T3 or T1 interface:[edit]user@host# edit interfaces interface-name (t3-options | t1-options)
- Configure the local loopback:[edit interfaces interface-name (t3-options | t1-options)] user@host# set loopback local
The following is an example of the name for a T1 channel 0, group 0, on a Multichannel DS3 port for a channelized DS3 to DS0 interface:
[edit interfaces ds-2/1/0:0:0 t3-options]
Note: In order to configure T3 options on the Multichannel DS3, you configure the first logical interfaces: ds-2/1/0:0:0 t3-options.
The following is an example of the name for a T1 channel on a Multichannel DS3 port for a channelized DS3 to DS1 interface:
[edit interfaces t1-2/1/1:0 t1-options] - Verify the configuration:user@host# show
For example:
[edit interfaces t1-2/1/1:0 t1-options]user@host# show loopback local; - Commit the configuration:user@host# commit
For example:
[edit interfaces t1-2/1/1:0 t1-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. |
Verify That the Interface Is Up
Purpose
Display the status of a DS1 or DS3 interface to determine whether the physical link is up or down.
Action
To verify that the status of the Multichannel DS3 interface is up, use one of the following Junos OS command-line interface (CLI) operational mode commands:
Sample Output
The following sample output is for a channelized DS3 to DS0 interface:
user@host> show interfaces ds-2/1/0:5:1
Physical interface: ds-2/1/0:5:1, Enabled, Physical link is Up
Interface index: 36, SNMP ifIndex: 133
Description: Customer
Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed: 64kbps, FCS: 16, Mode: M23,
Framing: ESF
Device flags : Present Running
Interface flags: Point-To-Point SNMP-Traps
Link flags : Keepalives
Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3
Keepalive: Input: 1 (00:00:06 ago), Output: 1 (00:00:06 ago)
Input rate : 0 bps (0 pps)
Output rate : 0 bps (0 pps)
DS1 alarms : None
DS3 alarms : None
DS1 defects : None
DS3 defects : None
Logical interface ds-2/1/0:5:1.0 (Index 14) (SNMP ifIndex 134)
Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
Protocol inet, MTU: 1500, Flags: None
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.140.196/30, Local: 192.168.140.197
The following sample output is for a channelized DS3 to DS1interface:
user@host> show interfaces t1-2/1/0:19
Physical interface: t1-2/1/0:19, Enabled, Physical link is Up
Interface index: 50, SNMP ifIndex: 59
Description: Customer
Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed: T1, Loopback: None, FCS: 16,
Mode: M23, Framing: ESF
Device flags : Present Running
Interface flags: Point-To-Point SNMP-Traps
Link flags : Keepalives
Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3
Keepalive: Input: 11 (00:00:06 ago), Output: 13 (00:00:04 ago)
Input rate : 741512 bps (224 pps)
Output rate : 1266528 bps (224 pps)
DS1 alarms : None
DS3 alarms : None
DS1 defects : None
DS3 defects : None
Logical interface t1-2/1/0:19.0 (Index 27) (SNMP ifIndex 125)
Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
Protocol inet, MTU: 1500, Flags: None
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.140.196/30, Local: 192.168.140.197
Meaning
The sample output shows that the physical link is up and there are no DS1 or DS3 alarms or defects. You should not see any DS1or DS3 alarms. You can check any interface on the Multichannel DS3 port.
Clear Interface Statistics
Purpose
You must reset the Multichannel DS3 interface statistics before initiating the ping test. Resetting the statistics provides a clean start so that previous input/output errors and packet statistics do not interfere with the current efforts to diagnose the problem.
Action
To clear all statistics for the interface, use the following Junos OS CLI operational mode command:
Sample Output
user@host> clear interfaces statistics DS1/1/0:0:0 user@host> user@host> clear interfaces statistics t1-1/1/0:0 user@host>
Meaning
This command clears the interface statistics counters for the Multichannel or T1 interface only.
| Note: After a Graceful Routing Engine switchover (GRES) you must run clear interface statistics again or interface statistics will display junk vales. |
Force the Link Layer to Stay Up
Purpose
To complete the loopback test, the link layer must remain up. However, Junos OS is designed to recognize that loop connections are not valid connections and to bring the link layer down. You need to force the link layer to stay up by making some configuration changes to the encapsulation and keepalives.
Force the link layer to stay up, follow these steps:
Configure Encapsulation to Cisco-HDLC
Action
To set the encapsulation on a T1 physical interface, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces interface-name
- Configure Cisco-HDLC:[edit interfaces interface-name ]user@host# set encapsulation cisco-hdlc
- Verify the configuration:user@host# show
For example:
[edit interfaces t1-0/1/1:8]user@host# show encapsulation hdlc; - Commit the change:user@host# commit
For example:
[edit interfaces t1-0/1/1:8]user@host# commit commit complete
Meaning
This command sets the interface encapsulation to the Cisco High-Level Data-Link Control (HDLC) transport protocol.
Configure No-Keepalives
Action
To disable the sending of link-layer keepalives on a channelized DS3 or DS0 interface, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit]user@host# edit interfaces interface-name
- Configure no-keepalives:[edit interfaces interface-name]user@host# set no-keepalives
- Verify the configuration:user@host# show
For example:
[edit interfaces t1-0/1/1:8]user@host# show no-keepalives; - Commit the change:user@host# commit
For example:
[edit interfaces t1-0/1/1:8]user@host# commit commit complete
Meaning
By setting no-keepalives, the link layer is forced to stay up. If the setting remains at keepalive, the router will recognize that the same link-layer keepalives are being looped back and will bring the link layer down.
Verify the Status of the Logical Interface
Purpose
To verify the status of the logical interface, use the following Junos OS CLI operational mode command:
Action
Sample Output
The following sample output is for a channelized DS3 to DS0 interface:
user@host> show interfaces ds-2/1/0:5:1
Physical interface: ds-2/1/0:5:1, Enabled, Physical link is Up
Interface index: 36, SNMP ifIndex: 133
Description: Customer
Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed: 64kbps, FCS: 16, Mode: M23,
Framing: ESF
Device flags : Present Running
Interface flags: Point-To-Point SNMP-Traps
Link flags : Keepalives
Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3
Keepalive: Input: 1 (00:00:06 ago), Output: 1 (00:00:06 ago)
Input rate : 0 bps (0 pps)
Output rate : 0 bps (0 pps)
DS1 alarms : None
DS3 alarms : None
DS1 defects : None
DS3 defects : None
Logical interface ds-2/1/0:5:1.0 (Index 14) (SNMP ifIndex 134)
Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
Protocol inet, MTU: 1500, Flags: None
Addresses, Flags: Is-Preferred Is-Primary
Destination: 10.10.10.196/30, Local: 10.10.10.197
The following sample output is for a channelized DS3 to DS1interface:
user@host> show interfaces t1-2/1/0:19
Physical interface: t1-2/1/0:19, Enabled, Physical link is Up
Interface index: 50, SNMP ifIndex: 59
Description: Customer
Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed: T1, Loopback: None, FCS: 16,
Mode: M23, Framing: ESF
Device flags : Present Running
Interface flags: Point-To-Point SNMP-Traps
Link flags : Keepalives
Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3
Keepalive: Input: 11 (00:00:06 ago), Output: 13 (00:00:04 ago)
Input rate : 741512 bps (224 pps)
Output rate : 1266528 bps (224 pps)
DS1 alarms : None
DS3 alarms : None
DS1 defects : None
DS3 defects : None
Logical interface t1-2/1/0:19.0 (Index 27) (SNMP ifIndex 125)
Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
Protocol inet, MTU: 1500, Flags: None
Addresses, Flags: Is-Preferred Is-Primary
Destination: 10.10.10.196/30, Local: 10.10.10.197
Meaning
The sample output shows that both channelized interfaces have the physical and logical links up.
Ping the Channelized Interface
Purpose
Use the ping command to verify the loopback connection.
Action
To ping the local interface, use the following Junos OS CLI operational mode commands:
Sample Output
user@host> ping interface t1-2/1/0:7 192.168.126.29
bypass-routing count 1000 rapid PING 192.168.126.29 (192.168.126.29 ): 56 data bytes !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! --- 192.168.126.29 ping statistics --- 1000 packets transmitted, 1000 packets received, 0% packet loss round-trip min/avg/max/stddev = 6.068/7.475/74.080/3.696 ms
Meaning
This command sends 1000 ping packets out of the channelized interface under the Multichannel DS3 port 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).
Check for 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 a channelized DS3 to DS0 interface:
user@host> show interfaces ds-2/1/0:5:1 extensive
Physical interface: ds-2/1/0:5:1, Enabled, Physical link is Up
Interface index: 36, SNMP ifIndex: 133, Generation: 35
Description: Customer
Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed: 64kbps, FCS: 16, Mode: M23,
Framing: ESF
Device flags : Present Running
Interface flags: Point-To-Point SNMP-Traps
Link flags : Keepalives
Hold-times : Up 0 ms, Down 0 ms
Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3
Keepalive statistics:
Input : 2 (last seen 00:00:05 ago)
Output: 2 (last sent 00:00:05 ago)
Statistics last cleared: 2002-08-01 10:14:45 UTC (00:00:16 ago)
Traffic statistics:
Input bytes : 524 304 bps
Output bytes : 528 304 bps
Input packets: 8 0 pps
Output packets: 8 0 pps
Input errors:
Errors: 0, Drops: 0, Framing errors: 0, Policed discards: 10, L3 incompletes: 0,
L2 channel errors: 0, L2 mismatch timeouts: 0, HS link CRC errors: 0
Output errors:
Carrier transitions: 0, Errors: 0, Drops: 0, Aged packets: 0
DS1 alarms : None
DS3 alarms : None
DS1 defects : None
DS3 defects : None
T1 media: Seconds Count State
SEF 0 0 OK
BEE 0 0 OK
AIS 0 0 OK
LOF 0 0 OK
LOS 0 0 OK
YELLOW 0 0 OK
BPV 0 0
EXZ 0 0
LCV 0 0
PCV 0 0
CS 0 0
LES 0
ES 0
SES 0
SEFS 0
BES 0
UAS 0
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
IDLE 0 0 OK
YELLOW 0 0 OK
BPV 0 0
EXZ 0 0
LCV 0 0
PCV 0 0
LES 0
PES 0
PSES 0
SEFS 0
UAS 0
Interface transmit queues:
B/W WRR Packets Bytes Drops Errors
Queue0 95 95 4 336 0 0
Queue1 5 5 1 22 0 0
HDLC configuration:
Giant threshold: 1514, Runt threshold: 3
Timeslots : 1
Byte encoding: Nx64K, Data inversion: Disabled
DS3 BERT configuration:
BERT time period: 0 seconds, Elapsed: 0 seconds
Algorithm: Unknown (0), Induced Error rate: 10e-0
DS1 BERT configuration:
BERT time period: 0 seconds, Elapsed: 0 seconds
Induced Error rate: 10e-0, Algorithm: 2^15 - 1, O.151, Pseudorandom (9)
PFE configuration:
Destination slot: 2, PLP byte: 2 (0x2f)
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 ds-2/1/0:5:1.0 (Index 14) (SNMP ifIndex 134) (Generation 13)
Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
Protocol inet, MTU: 1500, Flags: None, Generation: 20 Route table: 0
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.140.196/30, Local: 192.168.140.197, Broadcast: Unspecified,
Generation: 22
The following sample output is for a channelized DS3 to DS1 interface:
user@host> show interfaces t1-2/1/0:19 extensive
Physical interface: t1-2/1/0:19, Enabled, Physical link is Up
Interface index: 50, SNMP ifIndex: 59, Generation: 49
Description: Customer
Link-level type: Cisco-HDLC, MTU: 1504, Clocking: Internal, Speed: T1, Loopback: None, FCS: 16,
Mode: M23, Framing: ESF
Device flags : Present Running
Interface flags: Point-To-Point SNMP-Traps
Link flags : Keepalives
Hold-times : Up 0 ms, Down 0 ms
Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3
Keepalive statistics:
Input : 117 (last seen 00:00:08 ago)
Output: 121 (last sent 00:00:01 ago)
Statistics last cleared: 2002-08-01 10:14:45 UTC (00:19:38 ago)
Traffic statistics:
Input bytes : 22459734 236888 bps
Output bytes : 162288645 1322208 bps
Input packets: 201233 214 pps
Output packets: 236341 227 pps
Input errors:
Errors: 0, Drops: 0, Framing errors: 0, Policed discards: 377, L3 incompletes: 0,
L2 channel errors: 0, L2 mismatch timeouts: 0, HS link CRC errors: 0, SRAM errors: 0
Output errors:
Carrier transitions: 0, Errors: 0, Drops: 0, Aged packets: 0
DS1 alarms : None
DS3 alarms : None
DS1 defects : None
DS3 defects : None
T1 media: Seconds Count State
SEF 0 0 OK
BEE 0 0 OK
AIS 0 0 OK
LOF 0 0 OK
LOS 0 0 OK
YELLOW 0 0 OK
BPV 0 0
EXZ 0 0
LCV 0 0
PCV 0 0
CS 0 0
LES 0
ES 0
SES 0
SEFS 0
BES 0
UAS 0
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
IDLE 0 0 OK
YELLOW 0 0 OK
BPV 0 0
EXZ 0 0
LCV 0 0
PCV 0 0
LES 0
PES 0
PSES 0
SEFS 0
UAS 0
Interface transmit queues:
B/W WRR Packets Bytes Drops Errors
Queue0 95 95 234494 162020375 0 0
Queue1 5 5 164 5808 0 0
HDLC configuration:
Giant threshold: 1514, Runt threshold: 3
Timeslots : All active
Line encoding: B8ZS, Byte encoding: Nx64K, Data inversion: Disabled
DS3 BERT configuration:
BERT time period: 0 seconds, Elapsed: 0 seconds
Algorithm: Unknown (0), Induced Error rate: 10e-0
DS1 BERT configuration:
BERT time period: 10 seconds, Elapsed: 0 seconds
Induced Error rate: 10e-0, Algorithm: 2^15 - 1, O.151, Pseudorandom (9)
PFE configuration:
Destination slot: 2, PLP byte: 2 (0xab)
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 t1-2/1/0:19.0 (Index 27) (SNMP ifIndex 125) (Generation 26)
Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
Protocol inet, MTU: 1500, Flags: None, Generation: 34 Route table: 0
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.140.196/30, Local: 192.168.140.197, Broadcast: Unspecified, Generation: 44
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 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).
Diagnose a Suspected Circuit Problem
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.
Solution
To diagnose a suspected circuit problem, follow these steps:
- Create a Loop from the Router to the Network
- Create a Loop to the Router from Various Points in the Network
Create a Loop from the Router to the Network
To create a loop from the router to the network, follow these steps:
Loop the Entire T3 Interface Toward the Network
Purpose
Creating a loop from the entire T3 interface to the network allows the transport-layer engineer to test the router from various points in the network and isolate the problem.
Action
To create a loop from the entire T3 interface to the network, follow these steps:
- In configuration mode, go to the following hierarchy level:[edit] user@host# edit interfaces interface-name t3-options
- Configure the loopback:[edit interfaces interface-name t3-options] user@host# set loopback remote
- Verify the configuration:user@host# show
For example:
[edit interfaces t3-2/1/1:0 t3-options]user@host# show loopback remote; - Commit the configuration:user@host# commit
Meaning
The loopback remote command loops any traffic from the network back into the network.
The interface name is one of the following:
- T1 channel 0, channel group 0, on the Multichannel DS3 port for a channelized DS3 to DS0 interface (for example, ds-2/1/1:0:0)
- T1 channel 0 on the Multichannel DS3 port for a channelized DS3 to DS1 interface (for example, t1-2/1/1:0)
Loop a Particular T1 Channel Toward the Network
Purpose
Creating a loop from a particular T1 interface to the network allows the transport-layer engineer to test the T1 interface from various points in the network and isolate the problem.
Action
To create a loop from a particular T1 interface to the network, follow these steps:
- In configuration mode, go to the following hierarchy level:user@host# edit interfaces interface-name t1-options
- Configure the loopback:[edit interfaces interface-name t1-options]user@host# set loopback remote
- Verify the configuration:user@host# show
For example:
[edit interfaces ds-2/1/1:0:0 t1-options]user@host# show loopback remote; - Commit the configuration:user@host# commit
Meaning
This command loops any traffic from the network back into the network. The interface name is one of the following:
- Channel group 0 for the particular T1 channel on the Multichannel DS3 port for a channelized DS3 to DS3 interface (for example, ds-2/1/1:2:0)
- Particular T1 channel on the Multichannel DS3 port for a channelized DS3 to DS1 interface (for example, t1-2/1/1:3)
Create 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 Step 2 through Step 7 in Diagnose a Suspected Hardware Problem with a Multichannel DS3 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.
