Cisco Cisco IOS Software Release 12.0(19)S

Automatic Protection Switching (APS) allows switchover of traffic in the event of line failure. APS uses 
a 1+1 redundancy architecture: a “protect” POS interface in the network is configured as a backup for 
each “working” POS interface. When the working interface fails, the protect interface quickly assumes 
the traffic load. Normally, the protect and working interfaces are connected to a SONET ADM (add-drop 
multiplexer), which sends the same signal payload to the working and protect interfaces. 

This APS network survivability scheme is known in SDH networks as multiplexed switching protection 
(MSP). APS and MSP are fundamentally similar.

Complete the following steps to configure APS for concatenated ISE line cards:

See 

 for information on additional APS documentation. For configuration 

examples, see 

. 

The command aps authenticate can be used to ensure that only valid packets are accepted on the OOB 
communication channel. This command is recommended but not mandatory. If this feature is used, the 
same authenticate string must be configured on both the working and protect interfaces. Please check to 
make sure the authenticate strings on both working and protect interfaces remain identical whenever the 
command “aps protect 1 ip-address” is entered. 

Complete the following steps to configure the loopback to be associated with the working interface 
router. See 

 for an example 

configuration. 

Router(config)# interface loobacknumber

Selects the interface loopback.

Router(config-if)# ip address ip-address mask 

Specifies the IP address.

ip-address is the IP address 

mask is for the associated IP subnet

Router(config-if)# no ip directed-broadcast

Disables directed broadcast-to-physical broadcast 
translation on the interface.

Router(config-if)# no ip route-cache

Disables fast switching and autonomous switching.

Router(config-if)# no ip mroute-cache

Disables IP multicast fast switching.