4.1. Updating an Implementation of the IPv4-only IP-MIB
4.1. Updating an Implementation of the IPv4-only IP-MIB
The somewhat more specific changes that are required for IPv4 follow. Note well: this is not meant to be an exhaustive list and the reader should examine the MIB for full details.
Several of the general objects (ipForwarding, ipDefaultTTL, ipReasmTimeout) remain unchanged.
Most of the rest of the general objects were counters and have been moved into the ipSystemStatsTable. The basic instrumentation should remain the same, though the object definitions should be checked for clarifications. If they aren't already in a structure, putting the counter variables in one would be useful. Several new objects have been added to count additional items, and instrumentation code must be added for these objects. Finally, the SNMP routines must be updated to handle the new indexing.
In addition to the ipSystemStatsTable, the MIB includes the ipIfStatsTable. This table counts the same items as the system table but does so on a per interface basis. It is optional and may be ignored. If you decide to implement it, you may wish to arrange to collect the data on a per-interface basis and then sum those counters in order to provide the aggregate system level statistics. However, if you choose to provide the system level statistics by summing the interface level counters, no interface level statistics can be lost - if an interface is removed, the statistics associated with it must be retained.
The ipAddrTable has, loosely, been converted to the ipAddressTable. While the general idea remains the same, the ipAddressTable is sufficiently different that writing new code may be easier than updating old code. The primary difference is the addition of several new objects. In addition, the ipAdEntReasmMaxSize has been moved to another table, ipv4InterfaceTable. As above, the SNMP routines will need to be updated to handle the new indexing.
The ipNetToMediaTable has been moved to the ipNetToPhysicalTable. These tables are fairly similar and updating the old code may be straightforward. As above, the SNMP routines will need to be updated to handle the new indexing.
Two new tables, ipv4InterfaceTable and ipDefaultRouterTable, are required as well as several new ICMP counters.
Finally, there are several tables that are required for IPv6 but are optional for IPv4 that you may elect to implement.