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Cisco MGX 8850 Routing Switch Command Reference
Release 2.0, Part Number 78-10467-04 Rev C0, October 2001
Chapter2 Shelf Management Commands
cnfclksrc
•AXSM-sourced clocks r equire that the lines, port s , an d r e so urce partitioning have bee n c o nfi gu red.
•A switch can have one primary source and one secondary source.
•For each execution of cnfclksrc, you can spec ify only one clock source (either but not both primary
and secondary). Therefore, you must r ep eat cnf clksrc to specify the other clock source.
•If you do not to specify a seco ndar y s o urce , t he internal oscillator serves as th e s e co nd ary s o urce .
•For clock sources on the AXSMs, Cisco recommends that primary and secondary sources be on
separate cards or at least on s e pa rate lines.
•Revertive mode applies to only a primary BITS clock. For more details on the revertive option, see
the section, “Configuring a BITS Clock.”
•The switch constantly monitor s th e stat e o f th e clocks. For information on clo ck ala rm s , se e the
dspclkalms description.
Changing the Priority of a Cloc k Source
To change the priority of a clock source, the command sequence depends on the priority of the sources:
•To change the priority of a clock from primary to secondary or secondary to primary, you must first
execute delclksrc to deconfigure each s our ce .
•To change from one primary source to another primary source, you need to execute only cnfclksrc
for the new primary s ou r c e—th e system automatically deconfig ures the existing primary source.
Configuring a BITS Clock
You can configure a node to obtain its primary and secondary clocks through the BITS circuitry on the
PXM-UI S3. (The PXM-UI S3 ha s tw o co nnec tors to receive highly stable clock s f r om an ext er na l
device. The PXM-UI S3 can support st ra tu m l evels 1–3.) If the primary and secondary clocks are
externally-sourced, they must be th e s ame rate. For example, you cannot spec ify a T1 primary source
and an E1 secondary source.
Note Whenever the internal oscillator becom es t he primary or secondary source d ue to a fai lure , a minor
alarm is triggered on the lo cal node.
You can enable a revertive mode for the primary BITS clock. The revertive function on the PXM45
applies when the primary clock source fails. A failure is a loss of t he primary clock source after the n ode
has locked to that clock source. If a prim ary c lock r eco v e rs from a fail ur e and r e v ert i ve mode is e nabl ed,
the node automatically reverts to the primary source. The restored primary clock must be available for
12 seconds before it again becom es the active clock source.
If the primary clock source fails and revertive mode is disabled, you must re-configure the primary
source after the failure has be en co r re cte d.
To change the mode from revertive to non-revertive, execute cnfclk src. Follow the portID and pr io r it y
with “–revertive disable.”
Note For an E1 BITS clock, the curr en t p r od uct is automatically limi ted to two parameters of an E 1 li ne
that is used as a BITS source: twisted pair cabling and date-type signaling.
Related Commands
dspclksrcs, delclksrc, dspclkalms