Cisco Systems PA-4T Bedienungsanleitung PDF herunterladen (Seite 66)

Configuring Half-Duplex and Binary Synchronous Communications

PA-4T+ Synchronous Serial Port Adapter Installation and Configuration8-12

Conﬁguring CRCs

Cyclic redundancy check (CRC) is an error-checking technique that uses a calculated numeric value

to detect errors in transmitted data. All interfaces use a 16-bit CRC (CRC-CITT) by default, but also

support a 32-bit CRC. The sender of a data frame calculates the frame check sequence (FCS). Before

it sends a frame, the sender appends the FCS value to the message. The receiver recalculates the FCS

and compares its calculation to the FCS from the sender. If there is a difference between the two

calculations, the receiver assumes that a transmission error occurred and sends a request to the

sender to resend the frame.

To enable 32-bit CRC on an interface, specify the slot and port address of the interface followed by

the command crc 32. In the example that follows, the ﬁrst serial port on a PA-4T+ in port adapter

slot 1 of a Cisco 7200 series, Cisco uBR7200 series, or Cisco 7100 series router is conﬁgured for

32-bit CRC:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# interface serial 1/0

Router(config-if)# crc 32

Ctrl-Z

Router#

In the example that follows, the ﬁrst serial port on a PA-4T+ on a VIP2 in interface processor slot 3

is conﬁgured for 32-bit CRC:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# interface serial 3/1/0

Router(config-if)# crc 32

Ctrl-Z

Router#

To disable CRC-32 and return to the default CRC-16 (CRC-CITT) setting, specify the slot and port

address and use the no crc 32 command. For command descriptions, refer to the Conﬁguration

Fundamentals Conﬁguration Guide publication. If you need more information, see the “Cisco

Connection Online” section on page vii and the “Related Documentation” section on page vi.

If you are conﬁguring a PA-4T+ installed on the Cisco 7200 series router, proceed to the following

section “Conﬁguring Half-Duplex and Binary Synchronous Communications,” otherwise, proceed

to the “Checking the Conﬁguration” section on page 8-14.

Conﬁguring Half-Duplex and Binary Synchronous Communications

This section explains how to conﬁgure PA-4T+ interfaces for half-duplex and Bisync operation in

Cisco 7100 series and Cisco 7200 series routers.

Note Cisco IOS Release 11.2(7a)P or later supports half-duplex and bisync operation on PA-4T+

port adapters in Cisco 7200 series router.

Cisco IOS Release 12.0(3)T or later, or 12.0(1)XE or later support nonstandard clock rates on

PA-4T+ interfaces installed in Cisco 7204VXR and Cisco 7206VXR routers.

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Cisco Systems PA-4T Bedienungsanleitung Seite 66