Multicast Group Membership Discovery MIB
obsoletes
Extracted elements (28)
RFC 5519 obsoletes both RFC 2933 (IGMP MIB) and RFC 3019 (MLD MIB) by introducing a single unified Multicast Group Membership Discovery (MGMD) MIB that provides a generic interface for both IGMP (IPv4) and MLD (IPv6) implementations, eliminating the need to maintain two separate MIB modules.
Source list tables (mgmdHostSrcListTable and mgmdRouterSrcListTable) are provided as extensions to the cache tables to support source-specific multicast includes/excludes; this functionality is only available on IGMPv3- and MLDv2-capable nodes.
The mgmdRouterInterfaceProxyIfIndex object supports IGMP/MLD proxy devices used in simple topologies where running a full multicast routing protocol is unnecessary; a value of 0 indicates no proxying.
The MIB tables are indexed by both ifIndex and InetAddressType to allow a single physical interface to be configured in both IPv4 and IPv6 modes concurrently; the traffic on each address family is considered logically separate.
mgmdHostInterfaceVersion1QuerierTimer tracks the time remaining until the host assumes no IGMPv1 routers are present; while non-zero, an IGMPv2/v3 host replies to all queries with version 1 membership reports. This object is only present when mgmdHostInterfaceQuerierType is ipv4.
mgmdHostInterfaceVersion2QuerierTimer tracks time remaining until the MGMDv3 host assumes no MGMDv2 routers/hosts are present; while non-zero, the host replies with version 1 or 2 membership reports for backward compatibility.
mgmdRouterCacheVersion1HostTimer tracks time until the router assumes no IGMPv1 members remain; upon receiving any IGMPv1 Membership Report this timer resets to the group membership timer, and while non-zero the router ignores MGMDv2 Leave messages for that group. This timer applies only to IGMPv1 hosts, not MLD.
mgmdRouterCacheVersion2HostTimer tracks time until the router assumes no MGMDv2 members remain; applies to both IGMP and MLD hosts. Assuming no MGMDv1 hosts are detected, the router does not suppress MGMDv2 Leave messages when this timer is running.
Deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED; instead, SNMPv3 with cryptographic security SHOULD be deployed to protect access to read-write and read-create objects in this MIB.
Implementers SHOULD consider the security features provided by the SNMPv3 framework, including full support for SNMPv3 cryptographic mechanisms for authentication and privacy.
mgmdHostInterfaceVersion (Unsigned32 1..3) specifies the maximum MGMD version a host can run on an interface: 1 = IGMPv1 only, 2 = IGMPv2/MLDv1, 3 = IGMPv3/MLDv2. The default value is 3.
mgmdHostInterfaceVersion3Robustness (Unsigned32) controls the number of retransmissions of state-change reports by an MGMDv3 host: the report is sent [robustness - 1] additional times. The value must be non-zero; default is 2.
mgmdHostSrcListExpire and mgmdRouterSrcListExpire (TimeTicks) encode source list entry relevance: a non-zero value indicates an INCLUDE state entry, and a zero value indicates an EXCLUDE state entry.
mgmdRouterCacheExcludeModeExpiryTimer (TimeTicks) is applicable only to MGMDv3-compatible nodes and represents the time remaining before the EXCLUDE state expires and the interface transitions to INCLUDE mode. This value can never be greater than mgmdRouterCacheExpiryTime.
mgmdRouterInterfaceLastMemberQueryInterval (Unsigned32 0..31744, tenths of seconds, default 10) is the Max Query Response Interval inserted into group-specific queries sent in response to Leave Group messages; reducing it decreases leave latency. This value is irrelevant if mgmdRouterInterfaceVersion is 1.
mgmdRouterInterfaceQuerierExpiryTime (TimeTicks) gives the time remaining before the Other Querier Present Timer expires; if the local system is the querier, this object has value zero.
mgmdRouterInterfaceQueryInterval (Unsigned32 1..31744, seconds, default 125) specifies the frequency at which IGMP or MLD Host-Query packets are transmitted on an interface.
mgmdRouterInterfaceQueryMaxResponseTime (Unsigned32 0..31744, tenths of seconds, default 100) specifies the maximum query response interval advertised in MGMDv2 or IGMPv3 queries on the interface.
mgmdRouterInterfaceRobustness (Unsigned32 1..255, default 2) is the Robustness Variable that tunes for expected packet loss; IGMP and MLD are robust to (Robustness Variable - 1) packet losses.
mgmdRouterInterfaceVersion (Unsigned32 1..3) configures the MGMD version running on a router interface: 1 = IGMPv1, 2 = IGMPv2/MLDv1, 3 = IGMPv3/MLDv2. For IGMP and MLD to function correctly, all routers on a LAN must be configured to run the same version.
mgmdRouterInterfaceWrongVersionQueries (Counter32) counts general queries received whose IGMP or MLD version does not match mgmdRouterInterfaceVersion over the lifetime of the row; a non-zero value indicates a configuration error since all routers on a LAN must run the same version.
The MGMD MIB defines eight conceptual tables: mgmdHostInterfaceTable, mgmdRouterInterfaceTable, mgmdHostCacheTable, mgmdRouterCacheTable, mgmdInverseHostCacheTable, mgmdInverseRouterCacheTable, mgmdHostSrcListTable, and mgmdRouterSrcListTable, covering both host and router management objects.
The MGMD MIB module is assigned the OBJECT IDENTIFIER value { mib-2 185 }, recorded in the SMI Numbers registry under the descriptor mgmdStdMIB.
mgmdRouterInterfaceStatus (read-create) allows a remote user to enable or disable multicast support on a given router interface, presenting a significant denial-of-service vulnerability; secure access control is required.
mgmdRouterInterfaceVersion, mgmdRouterInterfaceQueryMaxResponseTime, mgmdRouterInterfaceRobustness, and mgmdRouterInterfaceLastMemberQueryInterval are tuning and protocol-conformance parameters whose compromise can be disruptive to local multicast communication or constitute a denial-of-service attack.
SNMP versions prior to SNMPv3 lack adequate security; even on a network secured with IPsec, there is no per-principal access control for GET/SET operations. Operators are responsible for configuring proper SNMPv3 access rights.
mgmdHostCacheSourceFilterMode and mgmdRouterCacheSourceFilterMode indicate whether an interface is in INCLUDE (1) or EXCLUDE (2) state for source filtering on MGMDv3/MLDv2-capable nodes. The router cache entry also exposes mgmdRouterCacheExcludeModeExpiryTimer, which transitions the interface from EXCLUDE back to INCLUDE when it expires.
InetAddress fields in all MGMD MIB tables use SIZE(4|16): 4 octets for IPv4 addresses and 16 octets for IPv6 addresses. The corresponding InetAddressType index (ipv4(1) or ipv6(2)) disambiguates the encoding, following RFC 4001.