Management Information Base (MIB)

Using the building blocks of SMI, objects are defined and given a place as nodes in the object tree. The object tree groups logically related objects together under a subtree. Such a subtree is called a Management Information Base (MIB). Each MIB (except for vendor-specific MIBs under the enterprises portion of the OID tree) has to be registered with an administrative authority, which in turn, assigns a unique OID to the root of the MIB subtree.

An example of a MIB is the Internet TCP/IP MIB, commonly referred to as MIB-II. It includes objects that are associated with TCP/IP variables and SNMP protocol variables. Other MIBs are defined for OSI protocols, Gateway protocols, and other protocols.

The SCO SNMP product supports the standard objects in the following MIBs that are readable and writable. In other words, all writable objects listed can be set and all readable objects can be retrieved using SCO SNMP.

• MIB-II (RFC 1213)

• IP Forwarding Table MIB (RFC 1354)

• Ethernet-like Interface Types MIB (RFC 1398)

• IEEE 802.5 Token-Rings MIB (RFC 1231)

• IETF Host Resources MIB (RFC1514) - must be enabled using mkdev hostmib.

SCO SNMP supports the readable objects in the following MIBs that can be retrieved with SNMP (none of the writable objects can be set).

• Link Control Protocol of PPP MIB (RFC 1471)

• IP Network Control Protocol of PPP MIB (RFC 1473)

• RIP Version 2 MIB Extension (RFC 1389)

The SCO SNMP product also supports all the objects under the SNMP Multiplexing (SMUX) group.

Each MIB is divided into logically related groups of objects. The important ones are: system, interfaces, tcp, udp, ip, egp, icmp, and snmp. These are also the groups under MIB-II. SCO SNMP supports MIB-II and can therefore manage all MIB-II objects.

Each object in the MIB has two important characteristics: its object identifier (OID) and its type. Object types are constructed from the fundamental types defined in the SMI.

The system group contains general information about the network node. An example of this is the physical location of the node, for example, ``R&D Facility, 3rd floor machine room.''

The interfaces group contains information about network interfaces, such as Ethernet^® and point-to-point links. Information is kept about such items as interface status (for example, up or down), packet counts, and so on.

The rest of the groups contain information about the particular protocol to which they refer. This includes items such as the number of packets received with a particular protocol type and the number of packets received with incorrect checksums.

See also:

• ``SMI: Structure of Management Information''

• ``Using the SNMP commands''

• ``Modifying SNMP variables''

• ``Viewing SNMP status''

Enabling the Host Resources MIB (RFC1514)

The IETF RFC1514 defines a Host Resources MIB for use with managing host systems with SNMP. By default, this is not enabled in SCO OpenServer Release 5. The following example details how to activate it.

1. Log in as root.

2. Associate the MIB system names with their numeric object identifier/ASN notation:
   
   cd /etc/sysadm.d
   post_mosy -i hostmib.defs -o hostmib.dfn

3. Enter the following command (which calls /etc/init.d/hostmib):
   
   mkdev hostmib

   Select option 1 to install. When the process completes, you see:

      Loading Host Resources MIB..........done
   

4. Restart the /etc/snmpd daemon by rebooting the system or killing and restarting the daemon manually with ps(C) and kill(C).

5. The /etc/snmpd.peers file should contain an entry for the hostmib as in this example:

      "hostmib"    1.3.6.1.4.1.32.99.1 "aintNoThing"
   

The output should be similar to the following sample excerpt:

   Name: hrSystemUptime.0
   Value: 118356496
   

   Name: hrSystemDate.0
   Value: 07 d0 03 0d   09 06 17 00   2d 00 00