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Cisco MGX 8850 (PXM1E/PXM45), Cisco MGX 8950, Cisco MGX 8830, and Cisco MGX 8880 Configuration Guide
Release 5.0.10, OL-3845-01 Rev. B0, August 16, 2004
Chapter 3 Provisioning PXM1E Communication Links
General PXM1E Configuration Procedures
Establishing Redundancy Between Two Lines with APS
Cisco MGX switches use Automatic Protection Switching (APS) to provide line fault tolerance. APS is
a component of SONET and is therefore available only on optical interfaces and STM-1 interfaces
(which are the electrical equivalent of SONET OC-3). The Cisco MGX 8850 (PXM1E/PXM45), Cisco
MGX 8950, Cisco MGX 8830, and Cisco MGX 8880 Hardware Installation Guide, Releases 2 Through
5, lists all the card types and shows which cards support APS.
When you configure APS, you must define a working line and a protection line for each redundant line
pair. The working line is the primary or preferred line, and communications take place over that line as
long as the line remains operative. Even when the working line and protection lines are on different cards
and a switchover occurs between the front cards, the working line remains active unless the working line
itself fails.
If a failure occurs on the working line, APS initiates a switchover to the protection line. The revertive
option allows you to control what happens when a failed working line recovers. If the revertive option
is enabled, the working line will become active after a configurable period of time. If the revertive option
is disabled, you must manually switch over from the protective line to the working line after the working
line recovers.
Cisco MGX switches support two types of APS: intracard APS and intercard APS. The following
subsections describe these two APS options, provide guidelines for planning APS configurations, and
describe how to configure APS.
Configuring Intracard APS Lines
Intracard APS configurations are created with the working and protection lines on the same back card
or in the same back card set. As shown in
, intracard APS makes it possible to have redundant
line protection for a standalone card configuration.
Figure 3-2
Standalone PXM1E with Intracard APS
When planning an intracard APS configuration on PXM1E cards, consider the following requirements:
•
APS is not supported on T1, E1, T3, and E3 interfaces.
•
The working line and the protection line must connect to adjacent ports on the same back card.
•
For all cards except VXSM-4-155, the working line must be assigned to an odd-numbered port. For
example, the working line could be line 1 and the protection line could be line 2.
PXM1E front card
OC-3c or OC-3c/DS3 combination back cards
Working line
8
0147
Midplane
Protection line
PXM-UI-S3/B back card
