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# t1 loopback

#### Syntax

t1 t1Channel loopback [ local | network { line | payload } ]

no t1 t1Channel loopback

t1 t1Channel loopback remote { line { fdl { ansi | bellcore } | inband } |
payload [ fdl ] [ ansi ] }

no t1 t1Channel loopback remote

#### Release Information

Command introduced before JUNOSe Release 7.1.0.

#### Description

Configures a loopback test for a T1 line on a CT3 module. The no version deactivates the loopback test; 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.

#### Options

- t1Channel—One or more individual T1 channels, ranges of T1 channels, or combination of individual channels and ranges, in the range 1–28 (no spaces); for example, 3,7-15,19-13,27
- 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. This is the default setting if you specify no optional keywords.
- network line—Loops the data back toward the network before the T1 framer and automatically sets a local loopback at the HDLC controllers
- network payload—Loops the payload data back toward the network at the T1 framer and automatically sets 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. The ansi keyword enables the remote line 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. The bellcore keyword enables the remote line FDL Bellcore bit loopback on the T1 channel, according to 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 FDL ANSI bit loopback on the T1 channel. You can optionally specify fdl and ansi, but it is not necessary.

#### Mode

Controller Configuration

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