Cisco Systems Cisco MGX 8850 Manuale Utente
2-20
Cisco MGX 8850 Routing Switch Command Reference
Release 2.0, Part Number 78-10467-04 Rev C0, October 2001
Chapter 2
Shelf Management Commands
cnfclksrc
cnfclksrc
Configure Clock Source—configure primary and secondary clocks and optional BITS clock
Configures a primary or secondary clock source for the node. A clock source can be:
•
An external device that connects to the PXM-UI S3 card
•
A line on an active AXSM
Clock Operation
When the switch first powers up, the internal oscillator on the PXM45 provides the clock to the node.
Thereafter, you configure the clock sources at each node according to a well-designed plan for network
synchronization. A typical configuration for an MGX 8850 network starts with a Building Integrated
Timing System (BITS) clock source of stratum 3 or higher on one node. Therefore, the node with the
BITS clock becomes the master clock source for the network. The active clock drives the clock line on
the backplane, and each service module takes its clock from this line. Thereafter, the clock goes out
through every line and is available as a configurable clock source on the other nodes.
Thereafter, you configure the clock sources at each node according to a well-designed plan for network
synchronization. A typical configuration for an MGX 8850 network starts with a Building Integrated
Timing System (BITS) clock source of stratum 3 or higher on one node. Therefore, the node with the
BITS clock becomes the master clock source for the network. The active clock drives the clock line on
the backplane, and each service module takes its clock from this line. Thereafter, the clock goes out
through every line and is available as a configurable clock source on the other nodes.
Currently, automatic propagation of a master clock through the network is not available. To propagate
the BITS-sourced clock to the other nodes, you execute cnfclksrc on the PXM45 at each node to specify
primary and secondary clocks derived from the AXSMs.
the BITS-sourced clock to the other nodes, you execute cnfclksrc on the PXM45 at each node to specify
primary and secondary clocks derived from the AXSMs.
(For a description of line-level looped timing, refer to the cnfln description the chapter, “
.” With looped timing, a clock arrives on a line and is redirected to become the
transmit clock for only that line.)
Prerequisites to Clock Configuration
Whether it uses BITS or an AXSM line for a clock source, the node first must have a network controller.
See the addcontroller description. For an AXSM-sourced clock, the additional prerequisites are:
See the addcontroller description. For an AXSM-sourced clock, the additional prerequisites are:
•
Activating the applicable line through upln
•
Creating logical ports through addport
•
Creating resource partitions through addrscprtn
Database Updates and Clock Configuration
If the node has a redundant PXM45, it automatically receives changes you make to the clock
configuration as well as automated clock changes that occur under node management. For example, if
you delete a clock source (delclksrc), the standby card automatically implements this configuration
change. Also, any switch from primary to secondary source is recorded by the standby PXM45.
configuration as well as automated clock changes that occur under node management. For example, if
you delete a clock source (delclksrc), the standby card automatically implements this configuration
change. Also, any switch from primary to secondary source is recorded by the standby PXM45.
Cards on Which This Command Runs
PXM45