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Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)
Chapter4 Configuring Interfaces Configuring the POS OC-12c Uplink Interface (Catalyst8540)
The value of the c2 byte is determined as follows:
•If the value of the c2 byte has not been explicitly configured with thepos flag command, the
SONET framer sends the following values:
–
For Cisco HDLC encapsulation with or without SPE scrambling: 0xCF
–
For PPP encapsulation with scrambling: 0x16 (RFC 2615)
–
For PPP encapsulation without scrambling: 0xCF (RFC 2615)
•If the valueof the c2 byte has been explicitly configured with the pos flag command, the configured
value is sent regardless of the encapsulation method.
The value of the s1s0 bits is determined as follows:
•If the value of the s1s0 bits have not been explicitly configured with thepos flag command, the
SONET framer sends the following values:
–
For SONET framing, the default value is 0.
–
For SDH framing, the default value is 2.
•If the value of the s1s0 bits have been explicitly configured with thepos flag command, the
configured value is used regardless of the framing.
Configuring POS SPE Scrambling
SONET payload scrambling applies a self-synchronous scrambler of polynomial X**43+1 to the
synchronous payload envelope (SPE) of the interface to ensure sufficient bit transition density. Both
ends of the connection must use the same scrambling algorithm.
To configure POS SPE scrambling, perform the following steps, beginning in global configuration
mode:
Command Purpose
Step1 Router(config)# interface pos
slot/subslot/interface
Router(config-if)#
Enters interface configuration mode and specifies the POS
interface to configure.
Step2 Router(config-if)# no pos
scramble-atm Disables payload scrambling on the interface. Payload
scrambling is on by default.
Step3 Router(config-if)# no shutdown Enables the interface with the previous configuration.