Controlling The S1 Sonet Overhead Byte; Running Loopbacks - Cisco 10000 Series Configuration Manual

Commands
The following example shows how to specify the B1 BER threshold crossing alarm value of 4:
Router(config)# interface atm 5/0/0
Router(config-if)# atm threshold b1-tca 4

Controlling the S1 SONET Overhead Byte

On Cisco 10000 series routers, ATM line cards run over SONET. In most situations, the default value for
the S1 SONET overhead byte (0x0) does not need to be changed. Refer to the SONET standards for
information about the possible values for the S1 SONET overhead byte and the definition of each value.
Controlling a Transmitted S1 Overhead Byte
In Cisco IOS Release 12.2(28)SB, use the pos flag s1-byte tx command in interface configuration mode
to control the transmission of the S1 SONET overhead byte.
pos flag s1-byte tx value
Where:
•
•
In the following example the S1 SONET overhead byte is set to 0xF:
pos flag s1-byte tx 0xF
Reacting to a Received S1 Overhead Byte
In Cisco IOS Release 12.2(28)SB, use the pos flag s1-byte rx-communicate command to direct the
router to switch the clock source to internal when it receives an S1 SONET overhead byte with a value
of 0xF. When the S1 SONET overhead byte changes from 0xF to any other value, the clock source reverts
back to the clock source specified in the user configuration.
The S1 overhead byte is ignored by the receiving router unless the pos flag s1-byte rx-communicate
command is issued.
pos flag s1-byte rx-communicate
no pos flag s1-byte rx-communicate
The following example directs the router to switch to internal clocking when it receives an S1 SONET
overhead byte with a value of 0xF:
pos flag s1-byte rx-communicate
The default for the pos flag s1-byte rx-communicate command is disabled or off.

Running Loopbacks

You can run a loopback by using the loopback command:
loopback {line | diagnostic {parallel | path | serial}}
no loopback {line | diagnostic {parallel | path | serial}}
Where:
•
•
•
Cisco 10000 Series Router Line Card Configuaration Guide
3-14
value is in the range of 0x0 to 0xF
0x0 is the default value
line is the line loopback
diagnostic starts an internal diagnostic loopback
parallel is the internal diagnostic parallel loopback
Chapter 3 1-Port OC-12 ATM Line Card Configuration
OL-8834-04