1.5 Assembling and Cabling WAN Components
1.5.6 Verifying central-site installation
Each central-site router has LED displays that allow you to verify that the router components are installed and functioning properly. For LED information that is specific to your router, refer to the installation and configuration guide that accompanied your router.

On the Cisco 3600 router, the LEDs on the front of the router enable you to determine router performance and operation, as shown in Figure . The ready LED indicates that a functional module has been installed in the indicated slot. If the LED is off, the slot is empty or the module is not functional. The active LED blinks to indicate network activity on the module installed in the indicated slot.

All network modules have an enable (EN) LED, which indicates that the module has passed its self-tests and is available to the router. Each Ethernet port has two LEDs, as shown in Figure . The activity (ACT) LED indicates that the router is sending or receiving Ethernet transmissions. The link LED indicates that the Ethernet port is receiving the link integrity signal from the hub (10BASE-T only).

Each PRI network module has four LEDs in addition to the enable LED, as shown in Figure . The LEDs and their descriptions follow:

  • REMOTE ALARM designates a remote alarm condition, meaning the far-end equipment has a problem with the signal it is receiving from the upstream equipment.
  • LOCAL ALARM designates a local alarm condition indicating a loss of signal, a loss of frame, or unavailability due to excessive errors.
  • LOOPBACK designates a loopback condition in which signals are sent and then directed back toward their source from some point along the communications path. Loopback tests are often used to test network interface usability.
  • CARRIER DETECT specifies that you received the carrier on the telephone company link that indicates whether an interface is active. 

Digital modem module, shown in Figure , has five LEDs in addition to the enable LED-one for each MICAŽ module bank. The LEDs blink during initialization. After the enable LED comes on, the MICA module LEDs indicate that the corresponding MICA module is functioning. If a MICA module fails its diagnostics or if no MICA module is installed in a position, its LED remains off.

Each port on the serial network module has the additional LEDs, as shown in Figure . Descriptions of the LEDs follow:

  • CN/LPConnect when green; loopback when yellow
  • RXCReceive clock
  • RXDReceive activity
  • TXCTransmit clock
  • TXDTransmit activity