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Chapter 1
Preparing for Configuration
Guidelines for Creating a Network Clock Source Plan
Clock synchronization in an ATM network is very important. If two switches have trouble synchronizing
their communications, traffic between the switches may have excessive errors or line failures. MGX
switches support two methods of network clock synchronization:
•
•
Both of these methods of clock synchronization are described in the sections that follow.
Manual clock configuration and NCDP configuration operate independently of one another. In other
Note
words, you can configure both versions of network clock sourcing on your network. However, only one
version can be enabled at a time. You cannot run your manual network clock configuration on your
network while NCDP is running, and vice-versa. However, both configurations are stored in the disk
database. Therefore, if you disable NCDP, the network reverts back to your original manual network
clock configuration. If you enable NCDP on that same network at a later point, the network will revert
back to the previous NCDP configuration.
Note
On Cisco MGX 8850 (PXM1E) and Cisco MGX 8830 switches, clock source configuration is done on
the PXM1E card and passed to other nodes over PXM1E lines. On Cisco MGX 8850 (PXM45) and
Cisco MGX 8950 switches, clock source configuration is done on a PXM45 card, and clock sourcing
information is passed to other nodes over NNI trunks connected to service modules.
Planning for Manual Clock Synchronization
In manual clock source configurations, you need to configure a primary and secondary clock source,
which are distributed throughout the network. All nodes have an internal Stratum-3 clock that serves as
a tertiary clock source. The secondary clock source takes over if the primary clock source fails, and the
tertiary clock source takes over if the secondary clock source fails. If no clock sources are configured,
the switch uses the internal Stratum-3 clock source. If only a primary clock source is configured, the
internal Stratum-3 clock takes over in the event of a primary clock source failure.
example network clock source topology.
Release 5.0.10, OL-3845-01 Rev. B0, August 16, 2004
manual
Network Clock Distribution Protocol (NCDP)
Cisco MGX 8850 (PXM1E/PXM45), Cisco MGX 8950, Cisco MGX 8830, and Cisco MGX 8880 Configuration Guide
Guidelines for Creating a Network Clock Source Plan
Figure 1-6
shows an
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Table of Contents
Troubleshooting
