PXM1 and VISM/VISM-PR Card Clocking Options

Table Of Contents

VISM/VISM-PR Card Clocking Options

PXM1 Card as Primary Clocking Source

VISM Card as Clocking Source

VISM-PR Card as Clocking Source

PXM1E or PXM45 Card as Primary Clocking Source

Revertive and Nonrevertive Clocking

VISM/VISM-PR Card Clocking Options

An MGX 8000 Series platform, consisting of PXM and VISM cards, should have one primary clocking source. To avoid conflicts and to ensure proper operation, the settings for clocking options in both card types are considered together. You must use one of the following primary clocking source options:

•PXM1, PXM1E, and PXM45 cards—Provide clocking for all VISM/VISM-PR cards in the chassis.

•VISM card—Provides clocking for the PXM1, which then provides clocking to the entire chassis.

•VISM-PR card—Provides clocking for the PXM1, PXM1E or PXM45 card, which then provides clocking to the entire chassis.

This section contains the following topics;

• PXM1 Card as Primary Clocking Source

• VISM Card as Clocking Source

• VISM-PR Card as Clocking Source

• PXM1E or PXM45 Card as Primary Clocking Source

• Revertive and Nonrevertive Clocking

PXM1 Card as Primary Clocking Source

Figure 0-1 shows the PXM card primary clocking source option in which the clock source originates at the PXM side of the VISM/PXM interface.

Figure 0-1 VISM Configured for Local Clocking

The PXM1 card option allows you to configure the clocking source origination from one of the following sources:

•An external BITS clock on the PXM1 T1 or E1 back card port.

•An external OC3 signal on a PXM1 SONET back card port.

•The PXM1 card internal crystal (default).

The internal crystal is the default and is set as the primary clock source automatically when power is applied to the chassis.

To use one of the other two clocking sources, complete the following steps:

Step 1 Use the cnfclksrc command to configure the clocking source—external BITS clock or external OC3 signal.

Step 2 Use the cnfln command to configure all VISM lines for local clocking.

The PXM card option makes the PXM the clock source for the all cards in the chassis. The VISM cards then use this clocking to provide clocking for their associated T1 or E1 lines. Refer to Chapter 7, "CLI Commands," for more information on VISM commands.

Refer to the Cisco MGX 8850 Installation and Configuration Guide and the Cisco MGX 8000 Series Switch Command Reference for information on the following PXM card clocking commands:

•cnfcbclk

•cnfextclk

•cnfsrmclksrc

•dspcbclk

•dspclkinfo

•dspclksrc

•dspcurclk

VISM Card as Clocking Source

You can configure the VISM card as a primary or secondary clocking source.

Figure 0-2 shows the VISM card primary clocking source option in which the clock source originates at the VISM side of the VISM/PXM1 interface.

Figure 0-2 VISM Configured for Loop Clocking

The VISM card option originates clocking from one of the T1 or E1 lines on one of the VISM cards.

To configure the VISM card as the primary or secondary clocking source, complete the following steps:

Step 1 Log in to the VISM card.

Step 2 Use the cnfln command to configure each of the T1 or E1 lines on for local clocking.

All of the lines must be configured for local clocking.

Step 3 Change card (cc) to the PXM1 card.

Step 4 To configure the VISM as a primary clocking source, enter the cnfclksrc command with the following parameters:
cvgmgx1a.1.7.PXM.a > cnfclksrc <slot.port> P

Replace <slot.port> with the VISM card slot number and line number 1. The P indicates that the VISM card is configured as a primary clocking source.

Note VISM card allows you to configure the clock source on line 1 only.

Step 5 To display the configured clock on the PXM1 card, enter the dspclkinfo command.

The following example shows the service module as the clocking source.
cvgmgx1a.1.7.PXM.a > dspclkinfo
****** Clock HW registers ********SEL_T1 = t1 SEL100 = ON SEL120 = OFF SEL75 = OFFNOEXTCLK = ON NOEXTCLK2 = OFF
priMuxClockSource = SERVICE_MODULE_PRI_CLKprevPriMuxClockSource = INTERNAL_OSCprimaryInbandClockSourceLineNum = 1secMuxClockSource = INTERNAL_OSCprevSecMuxClockSource = INTERNAL_OSCsecondaryInbandClockSourceLineNumber = 1currentClockSetReq = primarycurrentClockHwStat = primaryStratumLevel = STRATUM4PreviousClockHwStat = noneextClock1Present = NoextClock2Present = NoextClkConnectorType = RJ45extClkSrcImpedance = 100 Ohmsnternal Clock Status=0, Primary Clock Status=0Secondary Clock Status=0, Last inband Clock State=0last Inband Clock state= 0, Last External Clock Present = 1Last External Clock2 Present = 1

Step 6 To configure the VISM as a secondary clocking source, enter the cnfclksrc command with the following parameters:
cvgmgx1a.1.7.PXM.a > cnfclksrc <slot.port> S

Replace <slot.port> with the VISM card slot number and line number 1. The S indicates that the VISM card is configured as a secondary clocking source.

Note VISM card allows you to configure the clock source on line 1 only.

Step 7 To display the configured clock on the PXM1 card, enter the dspclkinfo command.

The following example shows the service module as a secondary clock source.
cvgmgx1a.1.7.PXM.a > dspclkinfo
****** Clock HW registers ********SEL_T1 = t1 SEL100 = ON SEL120 = OFF SEL75 = OFFNOEXTCLK = ON NOEXTCLK2 = OFF
priMuxClockSource = SERVICE_MODULE_PRI_CLKprevPriMuxClockSource = SERVICE_MODULE_PRI_CLKprimaryInbandClockSourceLineNum = 1secMuxClockSource = SERVICE_MODULE_SEC_CLKprevSecMuxClockSource = INTERNAL_OSCsecondaryInbandClockSourceLineNumber = 1currentClockSetReq = primarycurrentClockHwStat = secondaryStratumLevel = STRATUM4PreviousClockHwStat = primaryextClock1Present = NoextClock2Present = NoextClkConnectorType = RJ45extClkSrcImpedance = 100 OhmsInternal Clock Status=0, Primary Clock Status=0Secondary Clock Status=0, Last inband Clock State=0last Inband Clock state= 0, Last External Clock Present = 1Last External Clock2 Present = 1

VISM-PR Card as Clocking Source

The VISM-PR card allows you to configure primary and secondary clocking from the following sources:

•Network clock—the local clock for the PXM1, PXM1E, or PXM45 module

•Any VISM-PR T1 or E1 line

•On-board oscillator

To configure the VISM-PR card as the primary or secondary clocking source, complete the following steps:

Step 1 Log in to the VISM-PR card.

Step 2 Use the cnfln command to configure each of the T1 or E1 lines on for local clocking.

All of the lines must be configured for local clocking.

Step 3 Change cards (cc) to the PXM1, PXM1E, or PXM45 cards.

Step 4 Use the cnfclksrc command to configure the PXM, PXM1E, or PXM45 card as a service module primary or secondary clocking source and specify VISM and its clocking line as the clocking source.

Note VISM-PR card allows you to configure the clock source on any line.

Step 5 Use the dspclkinfo command to show the service module as a primary or secondary clocking source.

You cannot delete a line that is configured as the clock source. You must first configure the line to not be the clock source, and then you can delete the line.

Refer to Chapter 7, "CLI Commands," for more information on VISM commands.

PXM1E or PXM45 Card as Primary Clocking Source

Use the cnfncdpclksrc command to configure the PXM1E or PXM45 card as the primary clock source. Refer to the Cisco MGX 8850 Installation and Configuration Guide and the Cisco MGX 8000 Series Switch Command Reference for configuration instructions. Use the following commands to display and verify your configuration:

•dspncdpclkinfo

•dspncdpclksrc

Revertive and Nonrevertive Clocking

Clocking can be either revertive or nonrevertive. If your MGX switch is configured for a clock source from a BITS source or PXM line source and the source line goes into the alarm state, a revertive or nonrevertive recovery occurs.

•Revertive clocking—If a node is configured and the clock source fails (due to a physical failure such as a loss of signal, the clock frequency drifts out of specification, or a bad frequency), the node abandons the clock source and finds an alternate clock source. When the original clock source repairs, the node automatically reverts to using the original clock source.

•Nonrevertive clocking—Similar to revertive clocking, except that when the original clock source repairs, the node does not automatically revert to the original clock source.

Revertive and nonrevertive clocking depends upon the processor module back card used and the clocking source specified. See Table 0-1 to determine if your clocking is revertive or nonrevertive in your network configuration.

Table 0-1 Revertive/Nonrevertive Clocking and PXM Back Card Support

Processor Module Back Card

Using External Clock

Using Inband/Service Module Clock

PXM-UI

For loss of service: revertive

For bad frequency/drift: nonrevertive

For loss of service: revertive

For bad frequency/drift: nonrevertive

PXM-UI-S3

For loss of service: revertive

For bad frequency/drift: nonrevertive

For loss of service: revertive

For bad frequency/drift: nonrevertive

To make a nonrevertive clock source usable after it has failed, you must use the cnfclksrc command to remove the configuration of that particular clock source, and then use the cnfclksrc command again to configure it back. Refer to Chapter 7, "CLI Commands," for more information on CLI commands.

Processor Module Back Card	Using External Clock	Using Inband/Service Module Clock
PXM-UI	For loss of service: revertive For bad frequency/drift: nonrevertive	For loss of service: revertive For bad frequency/drift: nonrevertive
PXM-UI-S3	For loss of service: revertive For bad frequency/drift: nonrevertive	For loss of service: revertive For bad frequency/drift: nonrevertive