3Com 10014299 manual By default, loopback is disabled Set Frame Format

		CT3 Interface 151
Table 178 Set loopback mode of the CT3 interface
	Operation	Command
	Set loopback mode of CT3 interface	loopback { local payload
		remote }
	Disable loopback on the CT3 interface	undo loopback

Difference between two types of external loopback of the CT3 interface: Frame header overhead should be processed for external payload loopback (payload) while frame is not processed for external remote loopback (remote).

By default, loopback is disabled.

Single-channel loopback can be set on the T1 channels on a CT3 interface, and the settings of individual channels are independent.

Table 179 Set loopback mode of T1 channel

Operation	Command
Set loopback mode of T1 channel	t1 line-numberset loopback { local
	remote }
Disable loopback on the T1 channel	undo t1 line-numberset loopback

By default, loopback is disabled.

5Set Frame Format

Two frame formats are used on CT3 interface: M23 and C-bit. Perform the following configuration in CT3 interface view.

Table 180 Set frame format of the CT3 interface

Operation	Command
Set CT3 frame format	frame-format { c-bit m23 }
Restore the default setting	undo frame-format

By default, the CT3 interface uses the C-bit frame format.

When CT3 interface work in CT3 mode, single-channel frame format can be set on the T1 channels, and the settings of individual channels are independent.

Perform the following configurations in CT3 interface view.

Table 181 Set the frame format of T1 channel

Operation	Command
Set the frame format of T1 channel	frame-format { sf esf }
Restore the frame format of T1 channel to the	undo frame-format
default value

By default, the frame format of T1 channel is ESF.

6Configure Operate Mode of CT3 Interface

When setting the operating mode of a CT3 interface, you should set the operating modes of both the CT3 interface and the T1 channels on the interface.

Perform the following configuration in CT3 interface view.

Table 182 Set the operating mode of CT3 interface

Operation	Command
Configure Operate Mode of CT3 Interface	using { t3 ct3 }
Restore Operate Mode of CT3 Interface to default	undo using