Managing Your OSPF Network | OSPF Network Design Solutions

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A description of issues you might encounter when loading Cisco MIBs into your NMS is located at ftp://www.cisco.com/pub/mibs/app_notes/mib-compilers.

To access CCO via the WWW, use one of the following URLs:

   http://www.cisco.com/public/mibs    ftp://www.cisco.com/pub/mibs

OSPF MIBs

As previously described in Chapter 4, “Introduction to OSPF,” there are several RFCs that describe OSPF v2 MIBs (the most current of which is RFC 1850):

• RFC 1248

• RFC 1252

• RFC 1253

• RFC 1850

OSPF has a very large MIB, which provides you with a very powerful tool to monitor and configure the protocol. Figure 9-13 answers the question of where OSPF is located in the MIB tree.

Figure 9-13 OSPF MIB tree location.

The OSPF MIB as described in RFC 1850 has an impressive list of characteristics:

• 12 Distinct Tables

• 110 Management Variables

• 65 of the Management Variables are read only OSPF values

• 45 configurable Management Variables

No doubt you are wondering how to keep track of the 110 management variables for OSPF and why you would want to? This is a valid question as the amount of information made available to you through MIBs is impressive. It is true that most implementations of OSPF will not be concerned with every management variable but somewhere someone had a need so it has been included. The more commonly used variables are provided in Figure 9-14.

Figure 9-14 Detailed OSPF MIB tree.

Notes:
Figure 9-14 shows only the more commonly used OSPF MIB tables. The OSPFGENERALGROUP, OSPFAREATABLE, OSPFSTUBAREATABLE, OSPFHOSTTABLE, OSPFIFTABLE, OSPFIFMETRICTABLE, OSPFVIRTIFTABLE, and OSPFNBRTABLE tables contain read/write entries. The OSPFLSDBTABLE, OSPFAREARANGETABLE, and OSFPVIRTNBRTABLE tables are read-only.

As Figure 9-14 shows, eleven tables are most commonly used in OSPF implementations or those that have not yet completed the migration to the newer RFCs. There are actually twelve tables possible, but Cisco does not yet support them all, so that information will be saved for the 2nd edition. Please refer to RFC 1850 for additional information regarding the other tables not commonly used in OSPF implementations. The following list briefly discusses some of the characteristics of each table’s entries.

TIPS:
For purposes of this section, remember that MIBs are a type of database so the terminology used reflects this, such as table and row.

• OSPFGENERALGROUP. This table is referred to as a group since it only has one row that contains global OSPF parameters within that router (that is, OSPF version number or OSPF router ID).

• OSPFAREATABLE. Within this table there is a separate row for each OSPF area that a router belongs to. Each area is identified by the unique OSPF area value.

• OSPFSTUBAREATABLE. Within this table there is a separate row for each OSPF stub area that a router belongs to. Other characteristics that are important to the operation of OSPF in a stub area are included in this table, i.e. metric and area ID.

• OSPFLSDBTABLE. This table provides information on OSPF’s link state database. Each OSPF area is provided with a row for each LSA that is generated within that area. Needless to say this table can get very large as it also keeps track of the LSA sequence ID, type, age, checksum, etc.

• OSPFAREARANGETABLE. This table has become obsolete in the new RFC1850. Nevertheless, it is still commonly used. This table contains information regarding the IP address range of an OSPF area. Each area the router belongs to will have a row identified by the area ID.

• OSPFHOSTTABLE. This table identifies the hosts that are directly attached to the OSPF router. It provides information about these hosts such as IP address, metric and status.

• OSPFIFTABLE. This is another table that can get very large, as the MIB will create a row for each OSPF interface configured on a router. The OSPF authentication key is also stored here.

• OSPFIFMETRICTABLE. This table is very important as it contains the information regarding the OSPF cost of each interface. This information is then used to calculate the OSPF routing table.

• OSPFVIRTIFTABLE. This table contains all the virtual link information used within the router to include the area it will transit to and which other OSPF router it will connect to. It also holds the configurable OSPF information for a virtual link such as the OSPF timers, and authentication key.

• OSPFNBRTABLE. This table contains the OSPF neighbor information and each neighbor is uniquely identified by its IP address.

• OSPFVIRTNBRTABLE. This table is used by OSPF to monitor virtual link operation and events.

• OSPFAREARANGETABLE. This table is replaced in RFC 1850 by OSPFAREAAGGREGATETABLE, which creates a row for each range of IP addresses found within an OSPF area.

• OSPFEXTLSDBTABLE. A new table that has been added to the MIB, this table tracks all of the external LSAs that OSPF receives.

Configuring OSPF with MIBs

OSPF can be configured using the OSPF MIBs if desired, although it is not recommended unless you are very familiar with the OSPF MIB and both the SNMP and MIB operational characteristics. If not, then there is a very high chance you could cause severe problems in your network.

Because configuring OSPF through the router command line interface has been covered, this is by far the safest and most secure method. Therefore, it is not necessary to go into detail on how to duplicate this using the OSPF MIBs. Nevertheless, OSPF does come ready and willing to be configured in this manner. The MIBs are all set with some very accurate default values that, through minimal intervention on your behalf, can start the OSPF routing process.

Notes:
As a side note on this subject, I tried to configure a router to start the OSPF process, and the MIB was faster. But, when it came to configuring OSPF to my specific network environment (that is, when I needed to use loopback addresses or route summarization), the command line was faster. An interesting note is that when using the command line you have a variety of other features available that can enable you to double-check yourself and increase security.

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