3com MSR 20-20 참조 매뉴얼

cell: Internal cell loopback for checking that the local physical chip is operating.

local: Internal loopback for checking that the local service chip is operating.

payload: External payload loopback for checking that payload framing is normal.

remote: External loopback for checking that the remote end is normal.

Use the loopback command to configure the loopback mode on the ATM E1/T1 
interface.

Use the undo loopback command to disable loopback.

By default, loopback is disabled.

# Enable external payload loopback on ATM E1/T1 interface 5/0.

<Sysname> system-view

[Sysname] interface atm 5/0

[Sysname-Atm5/0] loopback payload 

min-active-links number

IMA group interface view

number: Number of links, in the range 1 to 8.

Use the min-active-links command to configure the minimum number of links 
required for the IMA group to work.

Use the undo min-active-links command to restore the default, that is, 1.

# Set the minimum number of links required for IMA group 1 to operate to 2.

<Sysname> system-view

[Sysname] interface atm 5/0

[Sysname-Atm5/0] ima ima-group 1

[Sysname-Atm5/0] interface ima-group 5/1

[Sysname-Ima-group5/1] min-active-links 2 

ATM E1/T1 interface view