SNMPv2 Management Information Base for the Internet Protocol using SMIv2
obsoleted by
- rfc-4293 — Management Information Base for the Internet Protocol (IP)
updates
- rfc-1213 — Management Information Base for Network Management of TCP/IP-based internets: MIB-II
Extracted elements (24)
This MIB module explicitly excludes management of IP routes; route management was separated into RFC 1354 (IP Forwarding Table MIB). The module description states: 'The MIB module for managing IP and ICMP implementations, but excluding their management of IP routes.'
The IP, UDP, and TCP MIB modules defined here support only IPv4. They use the IpAddress type defined as an OCTET STRING of length 4 to represent 32-bit IPv4 addresses and do not support 128-bit IPv6 addresses.
This MIB module updates RFC 1213 (MIB-II) by redefining its IP and ICMP objects using SMIv2. IP route management objects from MIB-II were separately updated by RFC 1354; the ipRouteTable OID { ip 21 } is marked obsolete in this module.
SNMPv2 entities implementing IP MUST implement both the ipGroup and icmpGroup as mandatory conformance groups, as stated in the MODULE-COMPLIANCE ipMIBCompliance.
Fragment reassembly counters include: ipReasmTimeout (max seconds fragments are held), ipReasmReqds (fragments needing reassembly), ipReasmOKs (successful reassemblies), and ipReasmFails (reassembly algorithm failures including timeouts and errors).
Fragmentation counters include: ipFragOKs (datagrams successfully fragmented), ipFragFails (datagrams that needed fragmentation but could not be, e.g., due to Don't Fragment flag), and ipFragCreates (fragments generated by fragmentation).
icmpInErrors counts ICMP messages received with ICMP-specific errors such as bad checksums or bad length. icmpOutErrors counts ICMP messages not sent due to ICMP-internal problems like buffer exhaustion, excluding IP-layer routing failures.
icmpOutRedirects will always be zero for hosts since hosts do not send ICMP Redirect messages; only routers send redirects.
ipAddrTable is a read-only table of IP addressing information for all IP addresses assigned to this entity, indexed by ipAdEntAddr (IpAddress).
ipDefaultTTL is a read-write INTEGER (1..255) giving the default value inserted into the Time-To-Live field of IP headers for datagrams originated at this entity when the transport layer does not supply a TTL.
ipForwarding is a read-write object indicating whether the entity acts as an IP router (forwarding=1) or not (notForwarding=2). It reflects whether the entity forwards datagrams not addressed to itself.
ipForwDatagrams counts datagrams for which this entity was not the final destination and a route was sought to forward them. On non-router hosts, this counts only successfully source-routed packets.
ipInAddrErrors counts input datagrams discarded because the destination IP address was not valid for this entity, including invalid addresses like 0.0.0.0, unsupported address classes (e.g., Class E), and non-local addresses on non-routing hosts.
ipInDiscards counts input IP datagrams that encountered no errors preventing processing but were discarded (e.g., for lack of buffer space). This counter excludes datagrams discarded while awaiting reassembly.
ipInReceives (Counter32) counts total input datagrams received from all interfaces including those received in error. ipInHdrErrors counts datagrams discarded due to IP header errors such as bad checksums, version mismatches, TTL exceeded, and bad options.
ipNetToMediaTable is the IP-to-physical address translation table (ARP cache), indexed by ipNetToMediaIfIndex and ipNetToMediaNetAddress, with read-create access allowing management stations to create and modify ARP entries.
ipRoutingDiscards counts valid routing entries chosen to be discarded, for example to free buffer space for other routing entries. It is assigned to { ip 23 }.
Setting ipNetToMediaType to invalid(2) invalidates the corresponding ARP entry. Agents may or may not remove invalidated entries from the table; management stations must be prepared to receive entries with ipNetToMediaType=invalid and interpret them accordingly.
The ICMP Group provides counters for each ICMP message type received and sent: icmpInMsgs and icmpOutMsgs give totals including errors; per-type counters cover DestUnreach, TimeExcd, ParmProb, SrcQuench, Redirect, Echo, EchoRep, Timestamp, TimestampRep, AddrMask, and AddrMaskRep.
icmpGroup (OBJECT-GROUP at ipMIBGroups 2) enumerates all mandatory ICMP managed objects covering both inbound and outbound counters for each ICMP message type.
ipGroup (OBJECT-GROUP at ipMIBGroups 1) enumerates all mandatory IP managed objects: ipForwarding, ipDefaultTTL, traffic counters (ipInReceives through ipFragCreates), ipAddrTable columns, ipNetToMediaTable columns, and ipRoutingDiscards.
Security issues are not discussed in this memo. The document defers all security considerations to the SNMPv2 administrative framework which defines authentication, authorization, access control, and privacy policies.
IpAddrEntry contains: ipAdEntAddr (IpAddress, index), ipAdEntIfIndex (INTEGER 1..2147483647, interface index per RFC 1573), ipAdEntNetMask (IpAddress, subnet mask with network bits=1 and host bits=0), ipAdEntBcastAddr (INTEGER 0..1, least-significant bit of broadcast address), and ipAdEntReasmMaxSize (INTEGER 0..65535, max reassemblable datagram size).
IpNetToMediaEntry contains: ipNetToMediaIfIndex (INTEGER, interface), ipNetToMediaPhysAddress (PhysAddress, hardware address), ipNetToMediaNetAddress (IpAddress, IP address), and ipNetToMediaType (INTEGER: other=1, invalid=2, dynamic=3, static=4).