4-10
Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
78-15224-02
Chapter 4 Configuring Interfaces
POS on the ML-Series card
C2 Byte and Scrambling
As listed in Table 4-2, POS interfaces use a value of 0x16 or 0xCF in the C2 byte depending on whether
ATM-style scrambling is enabled or not. RFC 2615, which defines PPP over SONET, mandates the use
of these values based on the scrambling setting. The RFC defines the C2 byte values as follows: “the
value of 22 (16 hex) is used to indicate PPP with X^43+ 1 scrambling [4]. For compatibility with
RFC 1619 (STS-3c-SPE/VC-4 only), if scrambling has been configured to be off, then the value 207 (CF
hex) is used for the Path Signal Label to indicate PPP without scrambling.”
In other words:
• If scrambling is enabled, POS interfaces use a C2 value of 0x16 (PPP and HDLC encapsulation).
• If scrambling is disabled, POS interfaces use a C2 value of 0xCF (PPP and HDLC encapsulation).
• LEX encapsulation uses a C2 value of 0x01 regardless of the scrambling setting.
Most POS interfaces that use a default C2 value of 0x16 (22 decimal) insert the pos flag c2 22 command
in the configuration, although this line does not appear in the running configuration since it is the default.
Use the pos flag c2 command to change the value from its default, as follows:
Router(config-if)# pos flag c2 ?
<0-255> byte value, default 0x16
Note Changing the C2 value from the default value does not affect POS scrambling settings.
Use the show run command to confirm your change. The show controller pos command outputs the
receive and transmit values and the C2 value. Thus, changing the value on the local end will not change
the value in the show controller command output.
Router# sh controllers pos 0
Interface POS0
Hardware is Packet/Ethernet over Sonet
PATH
PAIS = 0 PLOP = 0 PRDI = 0 PTIM = 0
PPLM = 0 PUNEQ = 0 PPDI = 0
BER_SF_B3 = 0 BER_SD_B3 = 0 BIP(B3) = 14 REI = 155
NEWPTR = 0 PSE = 0 NSE = 0
Active Alarms : None
Demoted Alarms: None
Active Defects: None
Alarms reportable to TCC/CLI: PAIS PRDI PLOP PUNEQ PPLM PTIM PPDI BER_SF_B3 BER_
SD_B3
Link state change defects: PAIS PLOP PRDI PPDI BER_SF_B3
Link state change time : 200 (msec)
DOS FPGA channel number: 0
Starting STS (0 based) : 0
Circuit size : STS-24c
RDI Mode : 1 bit
C2 (tx / rx) : 0x01 / 0x01
Framing : SONET
Path Trace
Mode : off
Buffer : Unstable
Remote hostname :
Remote interface:
Remote IP addr :
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