Usage Guidelines

CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data. The designators 16 and 32 indicate the length (in bits) of the frame check sequence (FCS). A CRC of 32 bits provides more powerful error detection, but adds overhead. Both the sender and receiver must use the same setting.

CRC-16, the most widely used error checking method throughout the United States and Europe, is used extensively with WANs. CRC-32 is specified by IEEE standard 802 and as an option by some point-to-point transmission standards. It is often used on Switched Multimegabit Data Service (SMDS) networks and LANs.

Usage Guidelines

The task ID hdlc (r,w) is required for use of the keyword hdlc . The task ID ppp(r,w) is required for use of the keyword ppp . The task ID fr(r,w) is required for use of the keyword frame-relay .

Usage Guidelines

Subinterfaces of a POS interface can only be configured using the l2transport keyword, if Frame Relay encapsulation is configured on the POS interface, using the encapsulation frame-relay command. Interfaces configured to use HDLC or PPP encapsulation cannot be configured using the l2transport keyword.

For the interface-path-id argument, use the following guidelines:

• If specifying a physical interface, the naming notation is rack/slot/module/port. The slash between values is required as part of the notation. An explanation of each component of the naming notation is as follows:

  • rack : Chassis number of the rack.

  • slot : Physical slot number of the line card.

  • module : Module number. A physical layer interface module (PLIM) is always 0.

  • port : Physical port number of the interface.

• f specifying a virtual interface, the number range varies, depending on interface type.

Usage Guidelines

HDLC keepalives require that the keepalive command is configured the same way on both routers. The two connected routers have no way of negotiating the keepalive value, because there is no way for the routers to tell each other what their configured values are. The keepalive value configured on each router (local and partner) sets the rate at which the Cisco IOS XR software sends packets. It also sets the rate at which the local end expects to receive incoming packets.

To set the keepalive value to the default value, use the keepalive command without specifying a value for the seconds argument.

If three keepalives are sent to the peer and no response is received from the peer, then the link makes the transition to the down state.

Usage Guidelines

When you issue the pos command in interface configuration mode for a POS interface, the CLI prompt changes to “config-if-pos” indicating that you have entered POS configuration submode. In the following sample output, the question mark (? ) online help function displays all the commands available under POS configuration submode:

RP/0/RSP0/CPU0:router(config)# interface POS 0/1/0/2 
RP/0/RSP0/CPU0:router(config-if)# POS 
RP/0/RSP0/CPU0:router(config-if-pos)# ?

  commit          Commit the configuration changes to running
  crc             Set the CRC on a POS interface
  describe        Describe a command without taking real actions
  do              Run an exec command
  exit            Exit from this submode
  no              Negate a command or set its defaults
  show            Show contents of configuration
  transmit-delay  Set POS transmit delay on an interface
   

Usage Guidelines

For the interface-path-id argument, use the following guidelines:

• If specifying a physical interface, the naming notation is rack/slot/module/port. The slash between values is required as part of the notation. An explanation of each component of the naming notation is as follows:

  • rack : Chassis number of the rack.

  • slot : Physical slot number of the line card.

  • module : Module number. A physical layer interface module (PLIM) is always 0.

  • port : Physical port number of the interface.

• If specifying a virtual interface, the number range varies, depending on interface type.

Usage Guidelines

No specific guidelines impact the use of this command.