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PA-POS-2OC3 Two-Port Packet-over-SONET Port Adapter Installation and Configuration
OL-3028-06
Chapter 4 Configuring the PA-POS-2OC3
Customizing the Configuration
Configuring Framing
The default framing value is SONET STS-3c.
Step 1
To configure for SDH STM-1, enter the
pos framing sdh
command:
Router(config)#
interface
pos 3/0
Router(config-if)#
pos framing sdh
Step 2
To change back to SONET STS-3c, enter the
no pos framing sdh
command.
Setting the Source of the Transmit Clock
The clocking default value specifies that the PA-POS-2OC3 use the recovered receive (RX) clock to
provide transmit (TX) clocking (called
loop timing
).
Note
If line loopback is selected, the PA-POS-2OC3 is forced into loop timing mode until the loopback is
disengaged.
Step 1
To specify that the Cisco PA-POS-2OC3 port adapter generate the transmit clock internally, enter the
clock source internal
command:
Router(config)#
interface
pos 3/0
Router(config-if)#
clock source internal
Step 2
To restore loop timing, enter the
no clock source internal
command or the
clock source line
command.
Configuring Cyclic Redundancy Checks
The cyclic redundancy check (CRC) default value is a 16-bit CRC (CRC-CITT). The CRC is an
error-checking technique that uses a calculated numeric value to detect errors in transmitted data. The
PA-POS-2OC3 also supports a 32-bit CRC. The sender of a data frame calculates the frame check
sequence (FCS). The sender appends the FCS value to outgoing messages. The receiver recalculates the
FCS and compares it to the FCS from the sender. If a difference exists, the receiver assumes that a
transmission error occurred and sends a request to the sender to resend the frame.
Step 1
To configure an interface for a 32-bit CRC, enter the
crc 32
command:
Router(config)#
interface
pos 3/0
Router(config-if)#
crc 32
Step 2
To disable the 32-bit CRC and return the interface to the default 16-bit CRC, enter the
no crc 32
command.
