Hardware manual

loopback (T1 interface)

IR-138

Cisco IOS Interface Command Reference

loopback (T1 interface)

To loop individual T1 channels on the Channelized T3 Interface Processor (CT3IP) in Cisco 7000

series routers with the RSP7000 and RSP7000CI and in Cisco 7500 series routers, use the loopback

interface conﬁguration command. Use the no form of this command to remove the loopback.

loopback [local | network {line | payload} | remote {line {fdl {ansi | bellcore}|inband} |

payload [fdl] [ansi]}]

no loopback

Syntax Description

Default

Disabled

Command Mode

Interface conﬁguration

Usage Guidelines

This command ﬁrst appeared in Cisco IOS Release 11.1 CA.

Use this command for troubleshooting purposes.

local (Optional) Loops the router output data back toward the router

at the T1 framer and sends an AIS signal out toward the

network.

network {line | payload} (Optional) Loops the data back toward the network before the

T1 framer and automatically sets a local loopback at the HDLC

controllers (line) or loops the payload data back toward the

network at the T1 framer and automatically sets a local

loopback at the HDLC controllers (payload).

remote line fdl {ansi |

bellcore}

(Optional) Sends a repeating, 16-bit ESF data link code word

(00001110 11111111 for FDL ANSI and 00010010 11111111

for FDL Bellcore) to the remote end requesting that it enter into

a network line loopback. Specify the ansi keyword to enable the

remote line Facility Data Link (FDL) ANSI bit loopback on the

T1 channel, per the ANSI T1.403 Speciﬁcation. Specify the

bellcore keyword to enable the remote SmartJack loopback on

the T1 channel, per the TR-TSY-000312 Speciﬁcation.

remote line inband (Optional) 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] (Optional) 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

Facility Data Link (FDL) ANSI bit loopback on the T1 channel.

You can optionally specify fdl and ansi, but it is not necessary.