PIM and IGMP

PIM and IGMP provide the current multicast behaviour surface. The model focuses on group membership, multicast reachability, and deterministic tree decisions.

Support level

Area	Level	Notes
IGMP membership	Behaviour model	Interface/group membership state can be configured and inspected.
PIM routing	Behaviour model	Solver-based multicast path construction for supported scenarios.
Sparse/dense detail	Partial	Current focus is lab reachability, not every PIM state machine.
Packet fidelity	Not modelled	No full multicast packet capture replay guarantee.

Standards coverage

Standard	Coverage	Notes
RFC 3376	Partial	IGMPv3-style membership concepts.
RFC 7761	Partial	PIM-SM concepts where required by the solver.

Feature matrix

Feature	Status	Notes
IGMP group state	Supported	Membership can feed multicast forwarding decisions.
PIM interface enable	Supported	Participating interfaces are represented.
RP configuration	Partial	Stored/used where implemented.
Multicast RPF	Behaviour model	Route-based path decisions are deterministic.
SSM	Not modelled	Source-specific multicast is not a current support claim.

Vendor command matrix

Command	IOS-style	Junos-style	VyOS-style	Notes
`ip igmp join-group 239.1.1.1`	Partial	n/a	Partial	Group membership intent.
`ip pim sparse-mode`	Partial	n/a	Partial	Interface participation.
`show ip igmp groups`	Supported	Partial	Partial	Membership view.
`show ip mroute`	Partial	Partial	Partial	Model-derived multicast route state.

Behaviour notes

The multicast model is intentionally conservative. It answers whether the configured topology can deliver group traffic in the supported scenarios, while avoiding claims about every join/prune packet transition.

Examples

Canonical example

configure terminal
interface GigabitEthernet0/0
 ip pim sparse-mode
 ip igmp join-group 239.1.1.1
end
show ip igmp groups
show ip mroute

Vendor styles

IOS-style

ip multicast-routing
interface GigabitEthernet0/0
 ip pim sparse-mode
 ip igmp join-group 239.1.1.1

Junos-style

set protocols pim interface ge-0/0/0.0 mode sparse
set protocols igmp interface ge-0/0/0.0

VyOS-style

set protocols pim interface eth0
set protocols igmp interface eth0

Known limits

MSDP, BSR, Auto-RP, SSM, register/register-stop fidelity, and detailed PIM timer races are not modelled.