# Chassis MIB representation

The Chassis MIB represents the boards installed in an NMS chassis. Boards and lines (trunks) are numbered sequentially and assigned to tables.

The Chassis agent detects each NMS board that is registered to NMS OAM and booted correctly, and monitors its operational status. The board model, type, revision, bus segment and slot, and logical ID are represented. Removing or inserting a board (Hot Swap) is also monitored, and traps are sent if the status of a board changes.

## Chassis MIB structure

There are five major tables within the Chassis MIB:

Table | Description
--- | ---
Chassis Configuration | Provides information about the chassis.
Bus Segment | Provides information about the bus segments in this chassis.
Board Access | Provides an index into the Bus Segment table and the Board table.
Board | Provides information about each board.
Board Access by backplane | Not implemented. (Reserved for future use.)

The following illustration shows the relationship between the tables in the Chassis MIB:

This illustration shows that a bus segment count value of 5 in the Chassis Configuration table results in five entries in the Bus Segment table. Bus segment 3 has four occupied slots, so there are four entries in the Board Access table for that bus segment. Each entry in the Board Access table has a boardIndex field, whose value is an index into the Board table for that board.

Two fields in the Board table match parts of dsx1CircuitIdentifier in the Trunk MIB. For more information about how the Chassis MIB and Trunk MIB can be used together, see Using the Chassis MIB.

The following illustration shows the sequence of objects in the Chassis MIB (with relative OIDs for table objects):