If you want to run loopback tests or bit error
rate tests on channelized T3 interfaces, you must enable testing at
the T3 or T1 layer. See Interface Stack for a description
of the layers.
For a list of the modules that support bit error
rate tests (BERTs) and remote loopback, see ERX Module Guide, Appendix A, Module Protocol Support.
Note:
BERTs are supported on frame-based channelized T3 interfaces,
with the exception of the CT3/T3 line module used with the 3-port
CT3/T3 I/O module.
Set the loopback to local to
test the line without connecting to the network.
host1(config-controll)#loopback local
Set the loopback to network to test the line connected to the network.
host1(config-controll)#loopback network line
(Optional) Configure one of the following tests for remote
loopback:
Set the loopback to remote to
request that a remote device connected on a T3 interface enter into
a loopback.
host1(config-controll)#loopback remote
Configure the T3 interface to enable or disable the ability
to enter into a loopback initiated by a remote device, as follows:
Issue the equipment customer loopback command to enable the router to enter into loopback when it receives
an appropriate signal from the remote device.
local—Loops the data
back toward the router; on supported line modules, also sends an alarm
indication signal (AIS) out toward the network
network—Loops the data
toward the network before the framer processes the data
payload—Loops the data
toward the network after the framer processes the data
remote—Sends a far end
alarm code in the C-bit framing, as defined in ANSI T1.404, to notify
the remote end to activate or (when you use the no version) deactivate the line loopback
Note:
Remote loopback is available only on channelized T3 interfaces
configured to use C-bit framing.
Example
host1(config-controll)#loopback local
Use the no version to restore
the default configuration, no loopback.
The T1 channel testing commands enable you to specify
testing parameters for a single channel, multiple individual channels,
ranges of channels, or any combination of the three types of specifications.
For example:
host1(config-controll)#t1 3,6-15,22,25-27
loopback local
To enable testing at the T1 layer:
Configure one of the following loopback tests.
Set the loopback to local to
test the line without connecting to the network.
host1(config-controll)#t1 2 loopback local
Set the loopback to network to test the line connected to the network.
host1(config-controll)#t1 2 loopback network
line
Set the loopback to remote-loopback to enable acceptance of loopback commands issued from a remote router.
host1(config-controll)#t1 2 remote-loopback
Configure the line to run bit error rate tests.
host1(config-controll)#t1 2 bert pattern 2^11
time 10 unframed
t1 bert
Use to enable bit error rate tests using the specified
pattern on a T1 interface.
Unlike other configuration commands, bert is not stored in NVRAM.
Specify one of the following test patterns:
Note:
The CT3/T3-F0 line module supports only the 2^11, 2^15, and 2^20-O153 options.
0s—Repetitive test pattern
of all zeros, 00000...
1s—Repetitive test pattern
of all ones, 11111...
2^11—Pseudorandom test
pattern, 2047 bits in length
2^15—Pseudorandom test
pattern, 32,767 bits in length
2^20-O153—Pseudorandom
test pattern, 1,048,575 bits in length
2^20-QRSS—Pseudorandom
QRSS test pattern, 1,048,575 bits in length
2^23—Pseudorandom test
pattern, 8,388,607 bits in length
alt-0-1—Repetitive alternating
test pattern of zeros and ones, 01010101...
Note:
The BERT patterns supported when testing the T1 layer vary depending
on the line module and I/O module assembly you are using.
Specify the duration of the test in the range 1–1440
minutes.
Optionally, specify the unframed keyword to overwrite
the framing bits.
Note:
The CT3/T3-F0 line module does not support the remote line inband option.
local—Loops the router
output data back toward the router at the T1 framer; on supported
line modules, also sends an alarm indication signal (AIS) out toward
the network
network { line | payload }—Specify the line keyword to loop the data back toward the network
before the T1 framer and automatically set a local loopback at the
HDLC controllers. Specify the payload keyword
to loop the payload data back toward the network at the T1 framer
and automatically set a local loopback at the HDLC controllers.
remote line fdl ansi—Sends
a repeating 16-bit ESF data link code word (00001110 11111111) to
the remote end requesting that it enter into a network line loopback.
Specify the ansi keyword to enable the
remote line facilities data link (FDL) ANSI bit loopback on the T1
channel, according to the ANSI T1.403 Specification.
remote line fdl bellcore—Sends
a repeating 16-bit ESF data link code word (00010010 11111111) to
the remote end requesting that it enter into a network line loopback.
Specify the bellcore keyword to enable
the remote line facilities data link (FDL) Bellcore bit loopback on
the T1 channel, per the Bellcore TR-TSY-000312 Specification.
remote line inband—Sends
a repeating 5-bit inband pattern (00001) to the remote end requesting
that it enter into a network line loopback
remote payload [ fdl ] [ ansi ]—Sends
a repeating, 16-bit, ESF data link code word (00010100 11111111) to
the remote end requesting that it enter into a network payload loopback.
Enables the remote payload facilities data link (FDL) ANSI bit loopback
on the T1 channel. You can optionally specify fdl and ansi.
If you do not specify an option, the router will set a
local loopback for the channel.
Example
host1(config-controll)#t1 2 loopback local
Use the no version to deactivate
loopback. If you specify the remote keyword,
the no version sends the 16-bit ESF data
link code word or inband pattern to deactivate the loopback at the
remote end based on the last activate request sent to the remote end.
If you do not specify the remote keyword,
the no version clears the local loopback
configuration.
