Cisco Systems Cisco MGX 8850 cnfclksrc

2-20

Cisco MGX 8850 Routing Switch Command Reference

Release 2.0, Part Number 78-10467-04 Rev C0, October 2001

Chapter2 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 th e PX M - U I S 3 car d

•A line on an active AXSM

When the switch first powers up, the internal oscillator on the PXM45 provides the clock to the node.

Thereafter, you configure the clock so urces at each node according to a well-designed plan for netwo rk

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 th e cl o ck lin e o n

the backplane, and each service module takes its clock from th is li ne . Th er ea fter, the clock goes out

through every line and is available as a co nfigu r ab le clo ck s o urce 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 oth er 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 chapte r, “Equipment and

Resource Provisioning.” With lo o pe d tim ing, a clock arrives on a li ne an d is redirected to becom e th e

transmit clock for only that line.)

Whether it uses BITS or an AXSM line for a clock sou rce, the nod e f irs t must ha ve a net wor k cont rol l er.

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

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 configu ratio n

change. Also, any switch from primary to secondary source is recorded by the standby PXM45.

Cards on Which This Command Runs

PXM45