Juniper Networks M160 manual Host Module, States for SFM LEDs Label Color Description

M160 Internet Router Hardware Guide

Table 7: States for SFM LEDs

Label	Color	State	Description
OK	Green	On steadily	SFM is functioning normally.
		Blinking	SFM is starting up.
FAIL	Amber	On steadily	SFM has failed.

Host Module

The host module constructs routing tables, performs system management functions, and generates the SONET/SDH clock signal for SONET/SDH interfaces. It consists of a paired Routing Engine and Miscellaneous Control Subsystem (MCS).

For a host module to function, both of its components—Routing Engine and MCS—must be installed and operational. One or two host modules can be installed into the midplane from the rear of the chassis, as shown in Figure 3: the Routing Engine slot labeled RE 0 is below the MCS slot labeled MCS 0 and the RE 1 slot is above the MCS 1 slot.

If two host modules are installed, both are powered on, but only one is active (the master); the second host module is in standby mode and performs no functions. By default, the master host module is the one with components installed in the RE 0 and MCS 0 slots. To change the default master Routing Engine, include the appropriate [edit chassis redundancy routing-engine]statement in the configuration, as described in the section about Routing Engine redundancy in the JUNOS Internet Software Configuration Guide: Getting Started.

The host module components are hot-pluggable, as described in Field-ReplaceableUnits (FRUs) on page 4. Removal or failure of one or both components in the standby host module does not affect router function. If one or both components in the master host module is removed from the chassis, the effect depends on whether two host modules are installed:

If there is only one host module, packet forwarding halts until both the Routing

Engine and MCS are reinstalled and functioning normally.

If there are two host modules, the effect depends on the software configuration:

If the Routing Engines are running JUNOS Release 6.0 or later and are configured for graceful switchover, the standby Routing Engine automatically assumes mastership without interruption of forwarding performance. For information about configuring graceful switchover, see the section about Routing Engine redundancy in JUNOS Internet Software Configuration Guide: Getting Started.

Otherwise, forwarding halts while standby host module becomes the master and the new master Routing Engine resets the Packet Forwarding Engine.

22 Host Module