2.5. A Closer Look at MIB-II MIB-II is a very important management group because every device that supports SNMP must also support MIB-II. Therefore, we will use objects from MIB-II in our examples throughout this book. We won't go into detail about every object in the MIB; we'll simply define the subtrees. The section of RFC1213-MIB that defines the base OIDs for the mib-2 subtree looks like this: mib-2 OBJECT IDENTIFIER ::= { mgmt 1 } system OBJECT IDENTIFIER ::= { mib-2 1 } interfaces OBJECT IDENTIFIER ::= { mib-2 2 } at OBJECT IDENTIFIER ::= { mib-2 3 } ip OBJECT IDENTIFIER ::= { mib-2 4 } icmp OBJECT IDENTIFIER ::= { mib-2 5 } tcp OBJECT IDENTIFIER ::= { mib-2 6 } udp OBJECT IDENTIFIER ::= { mib-2 7 } egp OBJECT IDENTIFIER ::= { mib-2 8 } transmission OBJECT IDENTIFIER ::= { mib-2 10 } snmp OBJECT IDENTIFIER ::= { mib-2 11 } mib-2 is defined as iso.org.dod.internet.mgmt.1, or 1.3.6.1.2.1. From here, we can see that the system group is mib-2 1, or 1.3.6.1.2.1.1, and so on. Figure 2-4 shows the MIB-II subtree of the mgmt branch. Figure 2-4. MIB-II subtree Table 2-5 briefly describes each management group defined in MIB-II. We don't go into great detail about each group since you can pull down RFC 1213 and read the MIB yourself. Table 2-5. Brief description of the MIB-II groupsSubtree name | OID | Description |
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system | 1.3.6.1.2.1.1 | Defines a list of objects that pertain to system operation, such as the system uptime, system contact, and system name. | interfaces | 1.3.6.1.2.1.2 | Keeps track of the status of each interface on a managed entity. The interfaces group monitors which interfaces are up or down and tracks such things as octets sent and received, errors and discards, etc. | at | 1.3.6.1.2.1.3 | The address translation (at) group is deprecated and is provided only for backward compatibility. | ip | 1.3.6.1.2.1.4 | Keeps track of many aspects of IP, including IP routing. | icmp | 1.3.6.1.2.1.5 | Tracks things such as ICMP errors, discards, etc. | tcp | 1.3.6.1.2.1.6 | Tracks, among other things, the state of the TCP connection (e.g., closed, listen, synSent, etc.). | udp | 1.3.6.1.2.1.7 | Tracks UDP statistics, datagrams in and out, etc. | egp | 1.3.6.1.2.1.8 | Tracks various statistics about the Exterior Gateway Protocol (EGP) and keeps an EGP neighbor table. | transmission | 1.3.6.1.2.1.10 | No objects are currently defined for this group, but other media-specific MIBs are defined using this subtree. | snmp | 1.3.6.1.2.1.11 | Measures the performance of the underlying SNMP implementation on the managed entity and tracks things such as the number of SNMP packets sent and received. |
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