| igmp.access_key | Access Key | Byte array | IGMP V0 Access Key |
| igmp.aux_data | Aux Data | Byte array | IGMP V3 Auxiliary Data |
| igmp.aux_data_len | Aux Data Len | Unsigned 8-bit integer | Aux Data Len, In units of 32bit words |
| igmp.checksum | Checksum | Unsigned 16-bit integer | IGMP Checksum |
| igmp.checksum_bad | Bad Checksum | Boolean | Bad IGMP Checksum |
| igmp.group_type | Type Of Group | Unsigned 8-bit integer | IGMP V0 Type Of Group |
| igmp.identifier | Identifier | Unsigned 32-bit integer | IGMP V0 Identifier |
| igmp.max_resp | Max Resp Time | Unsigned 8-bit integer | Max Response Time |
| igmp.max_resp.exp | Exponent | Unsigned 8-bit integer | Maxmimum Response Time, Exponent |
| igmp.max_resp.mant | Mantissa | Unsigned 8-bit integer | Maxmimum Response Time, Mantissa |
| igmp.mtrace.max_hops | # hops | Unsigned 8-bit integer | Maxmimum Number of Hops to Trace |
| igmp.mtrace.q_arrival | Query Arrival | Unsigned 32-bit integer | Query Arrival Time |
| igmp.mtrace.q_fwd_code | Forwarding Code | Unsigned 8-bit integer | Forwarding information/error code |
| igmp.mtrace.q_fwd_ttl | FwdTTL | Unsigned 8-bit integer | TTL required for forwarding |
| igmp.mtrace.q_id | Query ID | Unsigned 24-bit integer | Identifier for this Traceroute Request |
| igmp.mtrace.q_inaddr | In itf addr | IPv4 address | Incoming Interface Address |
| igmp.mtrace.q_inpkt | In pkts | Unsigned 32-bit integer | Input packet count on incoming interface |
| igmp.mtrace.q_mbz | MBZ | Unsigned 8-bit integer | Must be zeroed on transmission and ignored on reception |
| igmp.mtrace.q_outaddr | Out itf addr | IPv4 address | Outgoing Interface Address |
| igmp.mtrace.q_outpkt | Out pkts | Unsigned 32-bit integer | Output packet count on outgoing interface |
| igmp.mtrace.q_prevrtr | Previous rtr addr | IPv4 address | Previous-Hop Router Address |
| igmp.mtrace.q_rtg_proto | Rtg Protocol | Unsigned 8-bit integer | Routing protocol between this and previous hop rtr |
| igmp.mtrace.q_s | S | Unsigned 8-bit integer | Set if S,G packet count is for source network |
| igmp.mtrace.q_src_mask | Src Mask | Unsigned 8-bit integer | Source mask length. 63 when forwarding on group state |
| igmp.mtrace.q_total | S,G pkt count | Unsigned 32-bit integer | Total number of packets for this source-group pair |
| igmp.mtrace.raddr | Receiver Address | IPv4 address | Multicast Receiver for the Path Being Traced |
| igmp.mtrace.resp_ttl | Response TTL | Unsigned 8-bit integer | TTL for Multicasted Responses |
| igmp.mtrace.rspaddr | Response Address | IPv4 address | Destination of Completed Traceroute Response |
| igmp.mtrace.saddr | Source Address | IPv4 address | Multicast Source for the Path Being Traced |
| igmp.num_grp_recs | Num Group Records | Unsigned 16-bit integer | Number Of Group Records |
| igmp.num_src | Num Src | Unsigned 16-bit integer | Number Of Sources |
| igmp.qqic | QQIC | Unsigned 8-bit integer | Querier's Query Interval Code |
| igmp.qrv | QRV | Unsigned 8-bit integer | Querier's Robustness Value |
| igmp.record_type | Record Type | Unsigned 8-bit integer | Record Type |
| igmp.reply | Reply | Unsigned 8-bit integer | IGMP V0 Reply |
| igmp.reply.pending | Reply Pending | Unsigned 8-bit integer | IGMP V0 Reply Pending, Retry in this many seconds |
| igmp.s | S | Boolean | Supress Router Side Processing |
| igmp.type | Type | Unsigned 8-bit integer | IGMP Packet Type |
| igmp.version | IGMP Version | Unsigned 8-bit integer | IGMP Version |