Setup guide

5-19
Cisco 6400 Software Setup Guide
OL-1183-04
Chapter5 Redundancy and SONET APS Configuration
SONET APS for NLC Port Redundancy
SONET APS for NLC Port Redundancy
SONET automatic protection switching (APS) provides a mechanism to support redundant transmission
interfaces (circuits) between SONET devices. Automatic switchover from the working (primary) circuit
to the protection (secondary) circuit happens when the working circuit fails or degrades.
The Cisco 6400 supports SONET APS operation that is:
• 1+1— There is one working interface and one protection interface, and the same payload from the
transmitting end is sent to both the receiving ends. The receiving end decides which interface to use.
The line overhead (LOH) bytes (K1 and K2) in the SONET frame indicate both status and action.
• Linear—Back-to-back connection (as opposed to a ring topology), as defined in the Telcordia
GR-253-CORE document.
• Unidirectional—Transmit and receive channels are switched independently.
• Nonreverting—Nonreverting channels continue to operate after a failure has been corrected, thus
preventing data from flowing back to the working channel.
Note By default, the NLC in the lower slot number is the working device, and the NLC in the higher slot
number is the protection device.
Enabling and Disabling SONET APS
In the Cisco 6400, a pair of redundant ports is represented as a single interface. APS commands are
accepted only for an interface that represents a pair of redundant ports.
For APS operation, the APS mode must be specified for each interface associated with a redundant pair
of ports. To enable SONET APS, complete the following steps beginning in global configuration mode:
Note SONET APS is enabled by default when you install an NLC in a slot already configured for redundancy.
If the redundant NLC configuration is disabled by using the no associate slot or no associate subslot
redundancy configuration commands, two interface configuration sections are created, one for each port,
but all of the APS configuration commands are removed.
Example—Enabling SONET APS
In the following example, SONET APS is enabled for ATM interface 1/0/0:
!
interface atm 1/0/0
aps mode linear 1+1 nonreverting unidirectional
!
Command Purpose
Step1
Switch(config)# interface atm slot/subslot/port
Specifies the interface (that represents a pair of
redundant NLC ports).
Step2
Switch(config-if)# aps mode linear 1+1 nonreverting
unidirectional
Enables SONET APS on the interface. This command
must be entered before the other aps commands.