PIM6 - Protocol Independent Multicast for IPv6

PIM6 (Protocol Independent Multicast for IPv6) provides multicast routing in IPv6 networks, using MLD (Multicast Listener Discovery) instead of IGMP.

Overview

PIM6 is the version of the PIM protocol for IPv6 networks.

Key characteristics:

Multicast routing for IPv6
Uses MLD instead of IGMP
Supports PIM-SM (Sparse Mode) and PIM-SSM (Source-Specific Multicast)
Works with the IPv6 address space ff00::/8
Requires RP (Rendezvous Point) configuration for SM mode
Built-in support for Embedded RP (RFC 3956)

Standards:

RFC 4601 - Protocol Independent Multicast - Sparse Mode (PIM-SM): the base standard
RFC 7761 - Protocol Independent Multicast - Sparse Mode (PIM-SM): update
RFC 3810 - Multicast Listener Discovery Version 2 (MLDv2) for IPv6
RFC 3956 - Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address
RFC 4607 - Source-Specific Multicast for IP
RFC 5059 - Bootstrap Router (BSR) Mechanism for PIM

Use cases:

IPv6-only networks with multicast requirements
Modern data centers with IPv6
IoT networks based on IPv6
Video conferencing over IPv6
IPTV over IPv6
Software-defined networking (SDN) with IPv6 multicast

PIM6 vs PIM (IPv4)

Key differences

Characteristic	PIM (IPv4)	PIM6 (IPv6)
Group management	IGMP	MLD
Address space	224.0.0.0/4	ff00::/8
RP address	IPv4	IPv6, Embedded RP support
SSM range	232.0.0.0/8	ff3x::/32
Neighbor discovery	PIM Hello (IPv4)	PIM Hello (IPv6)
BSR address	IPv4	IPv6
Auto-RP	Available	Not applicable

Common features

Similar between PIM and PIM6:

The PIM-SM algorithm is identical
Bootstrap Router (BSR) mechanism
Source-Specific Multicast (SSM)
Register mechanism for new sources
Join/Prune messages
Assert mechanism for forwarder selection

MLD (Multicast Listener Discovery)

MLD overview

MLD is the IPv6 equivalent of IGMP.

MLD versions:

MLDv1 (RFC 2710):

Basic functionality
Listener Report and Listener Done messages
Any-Source Multicast (ASM)

MLDv2 (RFC 3810):

Source filtering (Include/Exclude)
Source-Specific Multicast (SSM) support
Backward compatibility with MLDv1

MLD messages

Multicast Listener Query:

Sent by the router to discover listeners
General Query - for all groups
Multicast-Address-Specific Query - for a specific group
Multicast-Address-and-Source-Specific Query - for a group and source (MLDv2)

Multicast Listener Report:

The host announces its intent to receive multicast traffic
Periodic updates

Multicast Listener Done (MLDv1):

The host leaves a multicast group
Fast subscription removal

MLDv2 Report:

Extended Report with source filtering
Include/Exclude modes

IPv6 Multicast addresses

IPv6 multicast structure: ffXY::/8

X - Flags:

0 = Well-known multicast
1 = Transient multicast

Y - Scope:

0 = Reserved
1 = Interface-local
2 = Link-local
4 = Admin-local
5 = Site-local
8 = Organization-local
E = Global

Special addresses:

ff02::1 - All Nodes (all nodes on the link)
ff02::2 - All Routers (all routers on the link)
ff02::5 - OSPFv3 All Routers
ff02::6 - OSPFv3 Designated Routers
ff02::9 - RIPng Routers
ff02::d - PIM Routers
ff02::16 - MLDv2 Reports destination
ff02::1:2 - All DHCP Servers and Relay Agents
ff05::1:3 - All DHCP Servers (site-local)

SSM range: ff3x::/32 (x = scope)

ff3e::/32 - SSM Global scope

Embedded RP: ff7x:0RP0::/96

The RP address is embedded in the multicast address

PIM6-SM (Sparse Mode)

Concept

PIM6-SM uses a shared tree through a Rendezvous Point (RP).

Operation stages:

The source registers:
- The source’s Designated Router (DR) encapsulates multicast packets in a PIM Register
- The Register is sent as unicast to the RP
Receivers join:
- The receiver’s DR sends a PIM Join toward the RP
- A shared tree (*, G) is built from the receivers to the RP
Shortest Path Tree (SPT):
- The receiver’s DR optionally switches to the SPT (S, G)
- A direct path from the source to the receiver
- Sends a Prune toward the RP for (*, G)
Optimization:
- The SPT minimizes latency
- The RP is offloaded once the SPT is built

RP for IPv6

RP configuration methods:

Static RP:
- Manual configuration on all routers
- Maximum control
- Requires synchronization
Embedded RP (RFC 3956):
- The RP address is embedded in the multicast group
- Automatic RP determination
- Format: ff7x:0RP0::/96
Bootstrap Router (BSR):
- Dynamic distribution of RP information
- Candidate-RP and Candidate-BSR
- Automatic updates

Embedded RP

Address format:

ff7S:0RPN:PPPP:PPPP:PPPP:PPPP:GGGG:GGGG

Where:

S - Scope (4 bits)
0 - Reserved (4 bits)
R - Riid (4 bits) - RP interface
P - Plen (8 bits) - RP prefix length
N - Network prefix (8 bits)
P…P - RP IPv6 prefix (64 bits)
G…G - Group ID (32 bits)

Example:

RP address: 2001:db8::1
Multicast group: ff75:0030:2001:0db8:0000:0000:0000:1234

Breakdown:
ff75 - flags=7 (transient), scope=5 (site-local)
0030 - Riid=0, Plen=48 (2001:db8::/48)
2001:0db8:0000 - RP prefix
0000:0000:1234 - Group ID

Advantages:

Does not require manual RP configuration on every router
The RP is determined automatically from the group
Simplified configuration

Disadvantages:

Limited flexibility in RP selection
Dependency on the addressing scheme

Basic PIM6 configuration

Enabling PIM6 on an interface

Syntax:

set protocols pim6 interface <interface>

Example:

set protocols pim6 interface eth0
set protocols pim6 interface eth1
set protocols pim6 interface eth2

commit
save

Effect:

Enables PIM6 on the interface
Automatically starts MLD
Sends/receives PIM Hello messages
Participates in multicast routing

Basic PIM6-SM network

Scenario:

Three routers in a triangular topology
Static RP on Router2
Multicast source behind Router1
Receivers behind Router3

Topology:

[Source] --- Router1 --- Router2 (RP) --- Router3 --- [Receivers]
             eth1         eth0  eth1     eth0  eth1

Router1 (First Hop Router):

# Interfaces
set interfaces ethernet eth0 address 2001:db8:12::1/64
set interfaces ethernet eth1 address 2001:db8:1::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# Static RP (must match on all routers)
set protocols pim6 rp address 2001:db8:2::1

commit
save

Router2 (RP):

# Interfaces
set interfaces ethernet eth0 address 2001:db8:12::2/64
set interfaces ethernet eth1 address 2001:db8:23::1/64
set interfaces ethernet eth2 address 2001:db8:2::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1
set protocols pim6 interface eth2

# RP on loopback or eth2
set protocols pim6 rp address 2001:db8:2::1

commit
save

Router3 (Last Hop Router):

# Interfaces
set interfaces ethernet eth0 address 2001:db8:23::2/64
set interfaces ethernet eth1 address 2001:db8:3::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# Static RP
set protocols pim6 rp address 2001:db8:2::1

commit
save

Verifying the basic configuration

Check PIM6 interfaces:

show ipv6 pim interface

Output:

Interface  State  Address            PIM Nbrs  PIM DR   DR Priority
eth0       up     2001:db8:12::1/64  1         2001:db8:12::2  1
eth1       up     2001:db8:1::1/64   0         local      1

Check PIM6 neighbors:

show ipv6 pim neighbor

Output:

Interface  Neighbor          Uptime     Holdtime  DR Priority
eth0       2001:db8:12::2    00:15:23   105       1

Check the RP:

show ipv6 pim rp-info

Output:

RP address       Group          Source          State
2001:db8:2::1    ff00::/8       Static          Active

MLD configuration

Enabling MLD on an interface

MLD is enabled automatically when PIM6 is activated, but you can tune its parameters.

View MLD groups:

show ipv6 mld groups

Output:

Interface        Address                    Group                   Uptime    Expires
eth1             2001:db8:3::1              ff3e::1234              00:05:23  00:04:12
eth1             2001:db8:3::1              ff05::5678              00:03:45  00:04:18

View MLD interfaces:

show ipv6 mld interface

Output:

Interface  State  Address            Version  Querier         Query Timer  Uptime
eth0       up     fe80::1            2        fe80::1         00:01:15     00:20:34
eth1       up     fe80::2            2        fe80::2         00:00:58     00:20:34

MLD parameters

Disable MLD on an interface:

set protocols pim6 interface <interface> mld disable

Use case:

The interface participates in PIM6 but does not process MLD
Used for transit interfaces without clients

Example:

set protocols pim6 interface eth0 mld disable

commit
save

Query Interval:

set protocols pim6 interface <interface> mld interval <seconds>

Parameters:

seconds: 1-65535 (default 125)

Example:

set protocols pim6 interface eth1 mld interval 60

commit
save

Last Member Query Count:

set protocols pim6 interface <interface> mld last-member-query-count <count>

Use case:

Number of Group-Specific Queries after a Listener Done
Affects the speed of removal from the group

Example:

set protocols pim6 interface eth1 mld last-member-query-count 2

commit
save

Last Member Query Interval:

set protocols pim6 interface <interface> mld last-member-query-interval <milliseconds>

Parameters:

milliseconds: 100-6553500 (default 1000)

Example:

set protocols pim6 interface eth1 mld last-member-query-interval 500

commit
save

Max Response Time:

set protocols pim6 interface <interface> mld max-response-time <milliseconds>

Use case:

Maximum time to wait for a response to a Query
Affects convergence

Example:

set protocols pim6 interface eth1 mld max-response-time 5000

commit
save

MLD Version:

set protocols pim6 interface <interface> mld version <1-2>

Use case:

Force the use of MLDv1 or MLDv2
MLDv2 is required for SSM

Example:

set protocols pim6 interface eth1 mld version 2

commit
save

Static group join

Join a group on an interface:

set protocols pim6 interface <interface> mld join <multicast-address>

Example:

set protocols pim6 interface eth1 mld join ff3e::1234

commit
save

Use case:

The router joins the group as a host
Useful for testing
The router begins receiving the group’s traffic on this interface

Join with a specified source (SSM):

set protocols pim6 interface <interface> mld join <multicast-address> source <source-address>

Example:

set protocols pim6 interface eth1 mld join ff3e::5678 source 2001:db8:100::10

commit
save

Use case:

Source-Specific Multicast
The router receives only from the specified source
Requires MLDv2

RP configuration

Static RP

RP address configuration:

set protocols pim6 rp address <ipv6-address>

Important: The configuration must be identical on all PIM6 routers in the domain.

Example:

set protocols pim6 rp address 2001:db8:100::1

commit
save

Verification:

show ipv6 pim rp-info

Output:

RP address       Group          Source          State
2001:db8:100::1  ff00::/8       Static          Active

RP for specific groups

RP for a range of groups:

set protocols pim6 rp address <ipv6-address> group <prefix>

Example:

set protocols pim6 rp address 2001:db8:100::1 group ff3e::/32
set protocols pim6 rp address 2001:db8:100::2 group ff05::/16

commit
save

Use case:

Different RPs for different groups
Load balancing between RPs
Separation by scope

Verification:

show ipv6 pim rp-info

Output:

RP address       Group          Source          State
2001:db8:100::1  ff3e::/32      Static          Active
2001:db8:100::2  ff05::/16      Static          Active

Keep-Alive Timer for the RP

Keep-Alive for (S,G) on the RP:

set protocols pim6 rp keep-alive-timer <seconds>

Parameters:

seconds: 31-60000 (default 185)

Use case:

The time (S,G) state is held on the RP
Affects convergence during changes

Example:

set protocols pim6 rp keep-alive-timer 210

commit
save

BSR (Bootstrap Router) for IPv6

BSR overview

BSR provides dynamic distribution of RP information.

Components:

Candidate-BSR (C-BSR):

A router that participates in BSR election
Selected based on priority and address
Distributes the RP-Set

Candidate-RP (C-RP):

A router that wants to be an RP
Sends a Candidate-RP-Advertisement to the BSR
The BSR includes it in the RP-Set

Bootstrap Message (BSM):

Contains the RP-Set
Distributed via multicast ff02::d
Flooded across the PIM6 domain

BSR configuration

Candidate-BSR:

set protocols pim6 rp candidate-bsr address <ipv6-address>
set protocols pim6 rp candidate-bsr priority <priority>

Parameters:

address: interface IPv6 address
priority: 0-255 (default 0, higher = better)

Example:

set protocols pim6 rp candidate-bsr address 2001:db8:100::1
set protocols pim6 rp candidate-bsr priority 100

commit
save

Candidate-RP:

set protocols pim6 rp candidate-rp address <ipv6-address>
set protocols pim6 rp candidate-rp priority <priority>
set protocols pim6 rp candidate-rp interval <seconds>

Parameters:

address: the IPv6 address that will be the RP
priority: 0-255 (default 192, lower = better for RP)
interval: 1-16383 (default 60) - the interval for sending C-RP Advertisements

Example:

set protocols pim6 rp candidate-rp address 2001:db8:100::1
set protocols pim6 rp candidate-rp priority 50
set protocols pim6 rp candidate-rp interval 30

commit
save

Candidate-RP for specific groups:

set protocols pim6 rp candidate-rp address <ipv6-address> group <prefix>

Example:

set protocols pim6 rp candidate-rp address 2001:db8:100::1 group ff3e::/32

commit
save

Verifying BSR

BSR information:

show ipv6 pim bsr

Output:

PIM6 Bootstrap Information
Current BSR Address: 2001:db8:100::1
Priority: 100
Hash Mask Length: 126
Expires: 00:01:45

Candidate BSR Address: 2001:db8:100::1
  Priority: 100
  Hash Mask Length: 126

RP-Set from the BSR:

show ipv6 pim rp-info

Output:

RP address       Group          Source          State      Priority  Holdtime
2001:db8:100::1  ff3e::/32      BSR             Active     50        150
2001:db8:100::2  ff05::/16      BSR             Active     100       150

SSM (Source-Specific Multicast) for IPv6

SSM overview for IPv6

SSM for IPv6 uses the ff3x::/32 range.

Address format:

ff3S::/32

Where S is the scope:

ff3e::/32 - Global SSM
ff35::/32 - Site-local SSM
ff38::/32 - Organization-local SSM

SSM advantages:

Does not require an RP
Direct (S,G) trees
Improved security
Less state on routers
Predictable traffic paths

SSM configuration

Automatic SSM detection: VyOS automatically uses SSM for ff3x::/32.

Explicit SSM range configuration:

set protocols pim6 ssm-range <prefix>

Example:

set protocols pim6 ssm-range ff3e::/32

commit
save

Verifying SSM:

show ipv6 pim state

The output will show (S,G) entries without (*,G) for SSM groups:

Source           Group            IIF      OIL
2001:db8:100::10 ff3e::1234       eth0     eth1, eth2

MLDv2 for SSM

SSM requires MLDv2 for source filtering.

Enabling MLDv2:

set protocols pim6 interface eth1 mld version 2

commit
save

Verification:

show ipv6 mld interface

Output:

Interface  State  Address            Version  Querier         Query Timer  Uptime
eth1       up     fe80::2            2        fe80::2         00:00:58     00:20:34

Advanced configuration

DR Priority

Setting the Designated Router priority:

set protocols pim6 interface <interface> dr-priority <priority>

Parameters:

priority: 0-4294967295 (default 1, higher = better)

Use case:

DR selection on a multi-access network
The DR registers sources and sends Joins

Example:

set protocols pim6 interface eth0 dr-priority 100

commit
save

Checking the DR:

show ipv6 pim interface eth0

Output:

Interface  State  Address            PIM Nbrs  PIM DR          DR Priority
eth0       up     2001:db8:12::1/64  1         2001:db8:12::1  100

Hello Interval

Setting the Hello interval:

set protocols pim6 interface <interface> hello <interval>

Parameters:

interval: 1-65535 seconds (default 30)

Use case:

The frequency of sending PIM Hello messages
Affects neighbor discovery

Example:

set protocols pim6 interface eth0 hello 15

commit
save

Join/Prune Interval

Setting the Join/Prune interval:

set protocols pim6 join-prune-interval <seconds>

Parameters:

seconds: 60-600 (default 60)

Use case:

The frequency of sending Join/Prune messages
Refresh for existing (S,G) and (*,G)

Example:

set protocols pim6 join-prune-interval 90

commit
save

Register Suppression Time

Setting the Register suppression time:

set protocols pim6 register-suppress-time <seconds>

Parameters:

seconds: 5-60000 (default 60)

Use case:

The time to suppress Register after a Register-Stop
The source’s DR stops encapsulation into Register

Example:

set protocols pim6 register-suppress-time 120

commit
save

Multicast Routing Table

SPT Switchover (iif): VyOS automatically switches to the SPT when traffic is received.

Infinity for the SPT Threshold: Disable switching to the SPT (stay on the shared tree):

set protocols pim6 spt-switchover infinity-and-beyond

Use case:

All traffic flows through the RP
Simplified topology
May increase latency

Example:

set protocols pim6 spt-switchover infinity-and-beyond

commit
save

Packet Parameters

DSCP for PIM packets:

set protocols pim6 packet dscp <value>

Parameters:

value: 0-63

Example:

set protocols pim6 packet dscp 46

commit
save

Configuration examples

Example 1: IPv6 Multicast in Yandex Cloud

Scenario:

VyOS router in Yandex Cloud as a PIM6 RP
Video server in the 2001:db8💯:/64 subnet
Three offices receive IPv6 multicast video
Using PIM6-SM with a static RP
SSM for critical streams

Topology:

[Video Server] --- eth1 --- [VyOS RP] --- eth0 --- [Internet/VPC]
  2001:db8:100::10                |
  ff3e::1234 (SSM)                |--- eth2 --- [Office 1]
  ff05::5678 (SM)                 |               2001:db8:1::/64
                                  |--- eth3 --- [Office 2]
                                  |               2001:db8:2::/64
                                  |--- eth4 --- [Office 3]
                                                  2001:db8:3::/64

VyOS RP configuration:

# Interfaces
set interfaces ethernet eth0 address 2001:db8:10::1/64
set interfaces ethernet eth0 description 'WAN - VPC Interconnect'

set interfaces ethernet eth1 address 2001:db8:100::1/64
set interfaces ethernet eth1 description 'DMZ - Video Servers'

set interfaces ethernet eth2 address 2001:db8:1::1/64
set interfaces ethernet eth2 description 'Office 1'

set interfaces ethernet eth3 address 2001:db8:2::1/64
set interfaces ethernet eth3 description 'Office 2'

set interfaces ethernet eth4 address 2001:db8:3::1/64
set interfaces ethernet eth4 description 'Office 3'

# Loopback for RP
set interfaces loopback lo address 2001:db8:999::1/128

# PIM6 on all interfaces
set protocols pim6 interface eth0
set protocols pim6 interface eth1
set protocols pim6 interface eth2
set protocols pim6 interface eth3
set protocols pim6 interface eth4

# MLD parameters for client interfaces
set protocols pim6 interface eth2 mld version 2
set protocols pim6 interface eth2 mld interval 60

set protocols pim6 interface eth3 mld version 2
set protocols pim6 interface eth3 mld interval 60

set protocols pim6 interface eth4 mld version 2
set protocols pim6 interface eth4 mld interval 60

# Disable MLD on WAN
set protocols pim6 interface eth0 mld disable

# RP configuration
set protocols pim6 rp address 2001:db8:999::1

# SSM range (automatic for ff3x::/32)
set protocols pim6 ssm-range ff3e::/32

# DR Priority on the server segment
set protocols pim6 interface eth1 dr-priority 100

# Firewall for IPv6 multicast
set firewall ipv6 input filter rule 100 action accept
set firewall ipv6 input filter rule 100 description 'Allow PIM6'
set firewall ipv6 input filter rule 100 protocol pim

set firewall ipv6 input filter rule 110 action accept
set firewall ipv6 input filter rule 110 description 'Allow MLD'
set firewall ipv6 input filter rule 110 protocol ipv6-icmp
set firewall ipv6 input filter rule 110 icmpv6 type 130-132

set firewall ipv6 input filter rule 120 action accept
set firewall ipv6 input filter rule 120 description 'Allow multicast traffic'
set firewall ipv6 input filter rule 120 destination address ff00::/8

# IPv6 Routing (OSPFv3 or BGP for unicast)
set protocols ospfv3 area 0 interface eth0
set protocols ospfv3 area 0 interface eth1
set protocols ospfv3 area 0 interface eth2
set protocols ospfv3 area 0 interface eth3
set protocols ospfv3 area 0 interface eth4
set protocols ospfv3 parameters router-id 10.0.0.1

commit
save

Office routers (example for Office 1):

# Interfaces
set interfaces ethernet eth0 address 2001:db8:1::254/64
set interfaces ethernet eth0 description 'To RP'

set interfaces ethernet eth1 address 2001:db8:10::100/64
set interfaces ethernet eth1 description 'Clients'

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# MLD on the client interface
set protocols pim6 interface eth1 mld version 2
set protocols pim6 interface eth1 mld interval 60

# RP (same as on the main router)
set protocols pim6 rp address 2001:db8:999::1

# SSM
set protocols pim6 ssm-range ff3e::/32

# OSPFv3 for unicast
set protocols ospfv3 area 0 interface eth0
set protocols ospfv3 area 0 interface eth1
set protocols ospfv3 parameters router-id 10.0.0.2

commit
save

Verification:

# On the RP
show ipv6 pim interface
show ipv6 pim neighbor
show ipv6 pim rp-info
show ipv6 pim state

# On the Office router
show ipv6 mld groups
show ipv6 pim join

# Traffic monitoring
tcpdump -i eth1 -n 'ip6 and dst net ff00::/8'

Example 2: PIM6-SSM for an IPv6-only network (VK Cloud)

Scenario:

IPv6-only network in VK Cloud
Only SSM (ff3e::/32) is used
No RP required
Video conferencing between offices
Sources in 2001:db8💯:/64

Topology:

[HQ Router] --- eth0 (2001:db8:10::1/64) --- [VK Cloud VPC]
     |                                              |
     eth1 (2001:db8:100::1/64)                     |
     |                                              |
[Video Server 2001:db8:100::10]            [Branch Router]
                                                    |
                                                    eth1 (2001:db8:200::1/64)
                                                    |
                                                [Users]

HQ Router:

# Interfaces
set interfaces ethernet eth0 address 2001:db8:10::1/64
set interfaces ethernet eth0 description 'VPC Interconnect'

set interfaces ethernet eth1 address 2001:db8:100::1/64
set interfaces ethernet eth1 description 'Video Servers'

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# Disable MLD on the server interface
set protocols pim6 interface eth1 mld disable

# SSM only (no RP needed)
set protocols pim6 ssm-range ff3e::/32

# DR Priority
set protocols pim6 interface eth1 dr-priority 100

# Firewall
set firewall ipv6 input filter rule 100 action accept
set firewall ipv6 input filter rule 100 protocol pim

set firewall ipv6 input filter rule 110 action accept
set firewall ipv6 input filter rule 110 destination address ff3e::/32

# BGP for unicast routing
set protocols bgp system-as 65001
set protocols bgp neighbor 2001:db8:10::254 address-family ipv6-unicast
set protocols bgp neighbor 2001:db8:10::254 remote-as 65000

commit
save

Branch Router:

# Interfaces
set interfaces ethernet eth0 address 2001:db8:10::100/64
set interfaces ethernet eth0 description 'VPC Interconnect'

set interfaces ethernet eth1 address 2001:db8:200::1/64
set interfaces ethernet eth1 description 'Users'

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# MLDv2 for clients (mandatory for SSM)
set protocols pim6 interface eth1 mld version 2
set protocols pim6 interface eth1 mld interval 60

# SSM only
set protocols pim6 ssm-range ff3e::/32

# Firewall
set firewall ipv6 input filter rule 100 action accept
set firewall ipv6 input filter rule 100 protocol pim

set firewall ipv6 input filter rule 110 action accept
set firewall ipv6 input filter rule 110 destination address ff3e::/32

# BGP
set protocols bgp system-as 65001
set protocols bgp neighbor 2001:db8:10::254 address-family ipv6-unicast
set protocols bgp neighbor 2001:db8:10::254 remote-as 65000

commit
save

Client subscription (Linux):

# SSM join: group ff3e::1234, source 2001:db8:100::10
smcroute -j eth0 2001:db8:100::10 ff3e::1234

# Or using socat
socat UDP6-RECV:5000,ipv6-join-source-group='[ff3e::1234]:[2001:db8:100::10]:eth0' STDOUT

Verification:

show ipv6 pim state
show ipv6 mld groups

Example 3: Embedded RP

Scenario:

Using Embedded RP to simplify configuration
RP address: 2001:db8:999::1/64
Groups: ff75:0040:2001:0db8:0999:0000::/96

RP Router:

# Interfaces
set interfaces loopback lo address 2001:db8:999::1/128

set interfaces ethernet eth0 address 2001:db8:10::1/64
set interfaces ethernet eth1 address 2001:db8:20::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# Embedded RP (automatic for ff7x::/16)
# No additional configuration required

commit
save

Client Router:

# Interfaces
set interfaces ethernet eth0 address 2001:db8:10::2/64
set interfaces ethernet eth1 address 2001:db8:100::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# Embedded RP - extracted automatically from the group address
# No manual RP configuration required

commit
save

Using an Embedded RP group: The application uses a group of the form:

ff75:0040:2001:0db8:0999:0000:0000:1234

Breakdown:

ff75 - flags=7 (transient), scope=5 (site-local)
0040 - Riid=0, Plen=64
2001:0db8:0999:0000 - RP prefix (2001:db8:999::/64)
0000:1234 - Group ID

Verification:

show ipv6 pim rp-info

Output:

RP address       Group                                  Source          State
2001:db8:999::1  ff75:40:2001:db8:999::/96              Embedded        Active

Example 4: BSR for dynamic RP

Scenario:

Two Candidate-RPs for redundancy
One BSR
Automatic distribution of RP information

BSR and Primary RP (Router1):

# Interfaces
set interfaces loopback lo address 2001:db8:100::1/128

set interfaces ethernet eth0 address 2001:db8:10::1/64
set interfaces ethernet eth1 address 2001:db8:20::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# BSR configuration
set protocols pim6 rp candidate-bsr address 2001:db8:100::1
set protocols pim6 rp candidate-bsr priority 100

# Candidate-RP configuration
set protocols pim6 rp candidate-rp address 2001:db8:100::1
set protocols pim6 rp candidate-rp priority 50
set protocols pim6 rp candidate-rp interval 30

commit
save

Secondary RP (Router2):

# Interfaces
set interfaces loopback lo address 2001:db8:100::2/128

set interfaces ethernet eth0 address 2001:db8:10::2/64
set interfaces ethernet eth1 address 2001:db8:30::1/64

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# Backup BSR (lower priority)
set protocols pim6 rp candidate-bsr address 2001:db8:100::2
set protocols pim6 rp candidate-bsr priority 50

# Candidate-RP (lower priority)
set protocols pim6 rp candidate-rp address 2001:db8:100::2
set protocols pim6 rp candidate-rp priority 100
set protocols pim6 rp candidate-rp interval 30

commit
save

Client Routers:

# PIM6 on the interfaces
set protocols pim6 interface eth0
set protocols pim6 interface eth1

# No static RP configuration!
# RP information is received via the BSR

commit
save

Verification:

show ipv6 pim bsr
show ipv6 pim rp-info

Operational commands

Show Commands

PIM6 interfaces:

show ipv6 pim interface

Output:

Interface  State  Address            PIM Nbrs  PIM DR          DR Priority
eth0       up     2001:db8:10::1/64  2         2001:db8:10::1  100
eth1       up     2001:db8:20::1/64  0         local           1

Interface details:

show ipv6 pim interface eth0

Output:

Interface eth0:
  State: up
  Address: 2001:db8:10::1/64
  PIM Neighbors: 2
  PIM DR: 2001:db8:10::1
  DR Priority: 100
  Hello Interval: 30s
  Generation ID: 0x12345678

PIM6 neighbors:

show ipv6 pim neighbor

Output:

Interface  Neighbor          Uptime     Holdtime  DR Priority  Generation ID
eth0       2001:db8:10::2    01:23:45   105       50           0xabcdef12
eth0       2001:db8:10::3    00:45:12   105       1            0x98765432

Neighbor details:

show ipv6 pim neighbor detail

RP information:

show ipv6 pim rp-info

Output:

RP address       Group          Source          State      Priority  Holdtime
2001:db8:100::1  ff00::/8       Static          Active     -         -
2001:db8:100::1  ff3e::/32      BSR             Active     50        150
2001:db8:999::1  ff75::/16      Embedded        Active     -         -

PIM6 state (multicast routes):

show ipv6 pim state

Output:

Installed Source           Group            IIF      OIL
1         2001:db8:100::10 ff3e::1234       eth0     eth1, eth2
1         *                ff05::5678       eth0     eth1

Details for a group:

show ipv6 pim state ff3e::1234

Join information:

show ipv6 pim join

Output:

Interface  Source           Group            State      Uptime     Expire   Prune
eth1       2001:db8:100::10 ff3e::1234       JOIN       00:15:23   00:00:45 -
eth0       *                ff05::5678       JOIN       00:10:12   00:00:38 -

BSR information:

show ipv6 pim bsr

Output:

PIM6 Bootstrap Information
Current BSR Address: 2001:db8:100::1
Priority: 100
Hash Mask Length: 126
Expires: 00:01:45

Candidate BSR Address: 2001:db8:100::1
  Priority: 100
  Hash Mask Length: 126

MLD groups:

show ipv6 mld groups

Output:

Interface        Address                    Group                   Uptime    Expires
eth1             2001:db8:3::1              ff3e::1234              00:05:23  00:04:12
eth1             2001:db8:3::1              ff05::5678              00:03:45  00:04:18

MLD interfaces:

show ipv6 mld interface

Output:

Interface  State  Address            Version  Querier         Query Timer  Uptime
eth0       up     fe80::1            2        fe80::1         00:01:15     00:20:34
eth1       up     fe80::2            2        fe80::2         00:00:58     00:20:34

MLD interface details:

show ipv6 mld interface eth1

Output:

Interface eth1:
  State: up
  Link-local Address: fe80::2
  Version: 2
  Querier: fe80::2 (local)
  Query Interval: 125s
  Query Timer: 00:00:58
  Other Querier Present Timer: 00:00:00
  Startup Query Interval: 31s
  Startup Query Count: 2
  Last Member Query Interval: 1000ms
  Last Member Query Count: 2
  Uptime: 00:20:34

MLD sources:

show ipv6 mld sources

Output (for MLDv2 SSM):

Interface  Group           Source           Timer    Flags
eth1       ff3e::1234      2001:db8:100::10 00:04:15 I

IPv6 Multicast Routing Table:

show ipv6 mroute

Output:

Source           Group            Proto  Input      Output     Packets  Bytes
2001:db8:100::10 ff3e::1234       PIM6   eth0       eth1       15234    45678901
                                                     eth2       12456    37890123
*                ff05::5678       PIM6   eth0       eth1       5678     12345678

Management Commands

Restart PIM6:

restart pim6

Clear PIM6 interfaces:

clear ipv6 pim interfaces

Clear PIM6 oil (Outgoing Interface List):

clear ipv6 pim oil

Troubleshooting

Neighbors do not come up

Problem: PIM6 neighbors are not visible.

Checks:

PIM6 enabled on the interfaces:
```
show ipv6 pim interface
```
IPv6 connectivity:
```
ping6 2001:db8:10::2
```
PIM Hello on the wire:
```
tcpdump -i eth0 -vv ip6 proto 103
```
You should see PIM Hello on ff02::d.

Firewall blocking PIM:

set firewall ipv6 input filter rule 100 action accept
set firewall ipv6 input filter rule 100 protocol pim
commit

Different Hello intervals: Make sure the Hello interval matches on both ends.
MTU issues:
```
show interfaces ethernet eth0
```
Check that the MTU is sufficient for IPv6 PIM packets.

RP does not resolve

Problem: RP information is missing.

Checks:

Static RP is configured:
```
show ipv6 pim rp-info
```
It should show the RP address.
RP is the same on all routers: Check the configuration on all PIM6 routers:
```
show protocols pim6 rp
```
BSR is working:
```
show ipv6 pim bsr
```
It should show the current BSR.

C-RP Advertisement reaches the BSR:

tcpdump -i eth0 -vv 'ip6 proto 103 and dst ff02::d'

Embedded RP format is correct: Check that the group is in the ff7x::/16 format and contains a valid RP prefix.

Traffic does not reach the receivers

Problem: Clients are subscribed, but do not receive multicast traffic.

Checks:

MLD groups are active:
```
show ipv6 mld groups
```
PIM Join was sent:
```
show ipv6 pim join
```
You should see a (*,G) or (S,G) Join.
Multicast routing table:
```
show ipv6 mroute
```
There should be an entry for the group.
PIM state:
```
show ipv6 pim state
```
Check the IIF and OIL.

Traffic on the incoming interface:

tcpdump -i eth0 -n 'ip6 and dst ff3e::1234'

RPF check passes:
```
show ipv6 route 2001:db8:100::10
```
The unicast route to the source should point to the IIF used for multicast.

Firewall allows multicast:

set firewall ipv6 input filter rule 120 action accept
set firewall ipv6 input filter rule 120 destination address ff00::/8
commit

SSM does not work

Problem: SSM groups do not receive traffic.

Checks:

Group is in the SSM range: It must be ff3x::/32 (for example ff3e::1234).

MLDv2 is enabled:

show ipv6 mld interface

The version must be 2.

If not:

set protocols pim6 interface eth1 mld version 2
commit

Client uses a source-specific join: On Linux:
```
smcroute -j eth0 2001:db8:100::10 ff3e::1234
```
(S,G) state exists:
```
show ipv6 pim state ff3e::1234
```
There should be an (S,G) entry, not (*,G).
RP is not configured for SSM: SSM does not require an RP. If there is an RP configuration for ff3x::/32, remove it:
```
delete protocols pim6 rp address <ipv6> group ff3e::/32
commit
```

Register packets do not reach the RP

Problem: The source is active, but the RP does not receive Register.

Checks:

DR is determined correctly:
```
show ipv6 pim interface eth1
```
The PIM DR should be the router connected to the source.
RP address is correct:
```
show ipv6 pim rp-info
```
Unicast route to the RP:
```
show ipv6 route 2001:db8:100::1
```
There should be a route to the RP.

Register on the wire:

tcpdump -i eth0 -vv 'ip6 proto 103 and dst 2001:db8:100::1'

You should see Register packets.

Firewall on the RP:

set firewall ipv6 input filter rule 100 action accept
set firewall ipv6 input filter rule 100 protocol pim
set firewall ipv6 input filter rule 100 source address 2001:db8::/16
commit

High CPU from PIM6

Problem: High CPU load on the router.

Causes and solutions:

Too many (S,G) entries:
```
show ipv6 pim state | wc -l
```
Consider moving to SSM or increasing resources.
Frequent Join/Prune: Increase the Join/Prune interval:
```
set protocols pim6 join-prune-interval 120
commit
```

Too frequent Hello: Increase the Hello interval:

set protocols pim6 interface eth0 hello 60
commit

Many MLD Queries: Increase the MLD interval:

set protocols pim6 interface eth1 mld interval 125
commit

Multicast traffic processed by the CPU: Check hardware offloading:
```
ethtool -k eth0 | grep offload
```

Monitoring and logging

Continuous Monitoring

Monitoring PIM6 neighbors:

watch -n 5 'show ipv6 pim neighbor'

Monitoring multicast routes:

watch -n 10 'show ipv6 mroute'

Monitoring MLD groups:

watch -n 5 'show ipv6 mld groups'

Packet capture for PIM6:

tcpdump -i eth0 -vv ip6 proto 103

Packet capture for MLD:

tcpdump -i eth1 -vv 'icmp6 and (ip6[40] == 130 or ip6[40] == 131 or ip6[40] == 132 or ip6[40] == 143)'

Packet capture for multicast traffic:

tcpdump -i eth1 -n 'ip6 and dst net ff00::/8'

A specific group:

tcpdump -i eth1 -n 'ip6 and dst ff3e::1234'

Logging

System logs:

show log tail 100 | match pim6

Syslog for protocols:

set system syslog global facility protocols level info
commit

External syslog:

set system syslog host 2001:db8:100::100 facility protocols level info
set system syslog host 2001:db8:100::100 port 514
commit

Debug logging (for troubleshooting):

set system syslog global facility protocols level debug
commit

Caution: Debug can generate a large volume of logs.

After troubleshooting, revert:

set system syslog global facility protocols level info
commit

Best practices

Network design

RP placement:
- Place the RP at the center of the network to minimize latency
- Use a loopback for the RP address (stability)
- Consider redundancy with BSR + multiple C-RPs
SSM vs SM:
- Use SSM (ff3x::/32) where possible
- SM only for Any-Source Multicast
- SSM does not require an RP and is more efficient
Embedded RP vs Static RP:
- Embedded RP to simplify configuration
- Static RP for full control
- BSR for dynamic RP in large networks
Scope selection:
- ff02::/16 - Link-local (single hop only)
- ff05::/16 - Site-local (within a site)
- ff08::/16 - Organization-local (the whole organization)
- ff0e::/16 - Global (the entire Internet)

Configuration

DR Priority:
- Set a high DR priority on the router closest to the source
- Controls who sends Register to the RP
Hello Interval:
- The default of 30 seconds is suitable for most networks
- Decrease it for faster convergence (CPU load)
- Increase it for stable networks with slow links
MLD Version:
- Use MLDv2 for SSM support
- MLDv1 only for legacy devices
PIM6 on all interfaces:
- Enable PIM6 on all interfaces participating in multicast
- Disable MLD on transit/upstream interfaces

Security

Firewall for PIM6:

set firewall ipv6 input filter rule 100 action accept
set firewall ipv6 input filter rule 100 protocol pim
set firewall ipv6 input filter rule 100 source address 2001:db8::/16

Restricting multicast groups:

set firewall ipv6 input filter rule 120 action accept
set firewall ipv6 input filter rule 120 destination address ff3e::/32
set firewall ipv6 input filter rule 120 description 'Allow only company SSM'

Rate limiting for MLD:

set firewall ipv6 input filter rule 110 action accept
set firewall ipv6 input filter rule 110 protocol ipv6-icmp
set firewall ipv6 input filter rule 110 icmpv6 type 130-132
set firewall ipv6 input filter rule 110 limit rate 10/second

Drop unknown multicast:

set firewall ipv6 input filter rule 999 action drop
set firewall ipv6 input filter rule 999 destination address ff00::/8
set firewall ipv6 input filter rule 999 description 'Drop unknown multicast'

Performance

SPT Switchover:
- By default, VyOS switches to the SPT immediately
- To reduce load on the RP, you can stay on the shared tree:
```
set protocols pim6 spt-switchover infinity-and-beyond
```
Register Suppression:
- Increase it to reduce the load on the DR:
```
set protocols pim6 register-suppress-time 120
```
Hardware Offloading:
- Enable it where available for multicast forwarding
- Check:
```
ethtool -k eth0 | grep offload
```

Resource monitoring:

show system resources
show ipv6 pim state | wc -l

Integration with other protocols

PIM6 + OSPFv3

Scenario: OSPFv3 for unicast, PIM6 for multicast.

# OSPFv3
set protocols ospfv3 area 0 interface eth0
set protocols ospfv3 area 0 interface eth1
set protocols ospfv3 parameters router-id 10.0.0.1

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1
set protocols pim6 rp address 2001:db8:100::1

commit

Important: PIM6 uses OSPFv3 unicast routes for the RPF check.

PIM6 + BGP

Scenario: BGP for IPv6 unicast, PIM6 for multicast.

# BGP
set protocols bgp system-as 65001
set protocols bgp neighbor 2001:db8:10::254 address-family ipv6-unicast
set protocols bgp neighbor 2001:db8:10::254 remote-as 65000

# PIM6
set protocols pim6 interface eth0
set protocols pim6 interface eth1
set protocols pim6 rp address 2001:db8:100::1

commit

Important: BGP routes are used for the RPF check in PIM6.

PIM6 + VPN (IPsec/WireGuard)

Scenario: Multicast through a VPN tunnel.

IPsec with VTI:

# VTI interface
set interfaces vti vti0 address 2001:db8:999::1/64

# PIM6 on VTI
set protocols pim6 interface vti0

# RP
set protocols pim6 rp address 2001:db8:100::1

commit

WireGuard:

# WireGuard interface
set interfaces wireguard wg0 address 2001:db8:888::1/64

# PIM6 on WireGuard
set protocols pim6 interface wg0

commit

Important: Multicast over VPN can have a performance impact.

PIM6 + IPv4 (Dual Stack)

Scenario: PIM for IPv4 and PIM6 for IPv6 simultaneously.

# PIM for IPv4
set protocols pim interface eth0
set protocols pim interface eth1
set protocols pim rp address 10.0.0.1

# PIM6 for IPv6
set protocols pim6 interface eth0
set protocols pim6 interface eth1
set protocols pim6 rp address 2001:db8:100::1

commit

Use case:

Dual-stack multicast
Migration from IPv4 to IPv6
Legacy applications (IPv4) + new ones (IPv6)

Comparing PIM6 with other solutions

PIM6 vs IGMP Proxy for IPv6

Characteristic	PIM6	IGMP/MLD Proxy
Complexity	High	Low
Topology	Any	Simple (tree)
Scalability	High	Limited
RP required	Yes (SM)	No
Redundancy	Full	Limited
Use case	Core/Data center	Edge/Branch

When to use PIM6:

Complex topology
Many sources
Data center multicast
Redundancy required

When to use MLD Proxy:

Simple topology (single source)
Branch office
IPTV from a provider
Limited resources

PIM6-SM vs PIM6-SSM

Characteristic	PIM6-SM	PIM6-SSM
RP required	Yes	No
Groups	ff00::/8 (except ff3x::/32)	ff3x::/32
(*,G) tree	Yes	No
(S,G) tree	Yes	Yes
Complexity	High	Low
Security	Medium	High
MLD Version	MLDv1/v2	MLDv2

When to use PIM6-SM:

Any-Source Multicast
Many dynamic sources
Legacy applications

When to use PIM6-SSM:

Known sources
Video distribution
IPTV, streaming
Improved security

Automation and scripts

Monitoring script

Bash script to check PIM6 neighbors:

#!/bin/bash

# pim6-monitor.sh
# Monitor PIM6 neighbors

LOG_FILE="/var/log/pim6-monitor.log"
EXPECTED_NEIGHBORS=2

check_neighbors() {
    local neighbor_count=$(vtysh -c "show ipv6 pim neighbor" | grep -c "eth0")

    if [ "$neighbor_count" -lt "$EXPECTED_NEIGHBORS" ]; then
        echo "$(date): WARNING - Only $neighbor_count neighbors, expected $EXPECTED_NEIGHBORS" >> "$LOG_FILE"
        return 1
    else
        echo "$(date): OK - $neighbor_count neighbors present" >> "$LOG_FILE"
        return 0
    fi
}

check_neighbors

vtysh -c "show ipv6 pim neighbor"
vtysh -c "show ipv6 pim interface"

Installing in cron:

*/5 * * * * /usr/local/bin/pim6-monitor.sh

RP failover script

Script to check RP availability:

#!/bin/bash

# rp-watchdog.sh
# Check the RP and switch to the backup

PRIMARY_RP="2001:db8:100::1"
BACKUP_RP="2001:db8:100::2"
LOG_FILE="/var/log/rp-watchdog.log"

check_rp() {
    if ping6 -c 3 -W 2 "$PRIMARY_RP" > /dev/null 2>&1; then
        return 0
    else
        return 1
    fi
}

if ! check_rp; then
    echo "$(date): Primary RP $PRIMARY_RP unreachable, switching to backup" >> "$LOG_FILE"

    vtysh << EOF
configure terminal
protocols pim6 rp address $BACKUP_RP
commit
save
exit
EOF

    echo "$(date): Switched to backup RP $BACKUP_RP" >> "$LOG_FILE"
else
    echo "$(date): Primary RP $PRIMARY_RP is reachable" >> "$LOG_FILE"
fi

References and resources

RFC Documents

RFC 4601 - Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification
RFC 7761 - Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (update)
RFC 3810 - Multicast Listener Discovery Version 2 (MLDv2) for IPv6
RFC 2710 - Multicast Listener Discovery (MLD) for IPv6
RFC 3956 - Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address
RFC 4607 - Source-Specific Multicast for IP
RFC 5059 - Bootstrap Router (BSR) Mechanism for Protocol Independent Multicast (PIM)
RFC 4291 - IP Version 6 Addressing Architecture

VyOS Documentation

Useful tools

FRRouting (FRR) - the routing suite used by VyOS for PIM6
smcroute - Static multicast routing tool
iperf3 - Network performance testing (multicast mode)
tcpdump - Packet capture
Wireshark - Packet analyzer
VLC - Media player with multicast support

Community

Next steps

After configuring PIM6, we recommend studying:

PIM (IPv4) - for IPv4 multicast
IGMP Proxy - for simple IPv4 multicast scenarios
OSPFv3 - for IPv6 unicast routing
BGP - for IPv6 BGP routing
Firewall - for protecting multicast networks
QoS - for prioritizing multicast traffic

Conclusion

PIM6 provides efficient multicast routing in IPv6 networks. Proper RP configuration, using SSM for known sources, and integration with MLD ensure stable operation of modern multicast applications in Yandex Cloud and VK Cloud.

Key takeaways:

PIM6 works with MLD instead of IGMP
An RP is required for PIM6-SM, but not for SSM
SSM (ff3x::/32) is recommended for most scenarios
Embedded RP simplifies configuration
BSR provides dynamic distribution of RP information
Firewall and security are critical for production
Monitoring neighbors, the RP, and multicast routes is mandatory

Reviewed by OpenNix LLC · Last updated on 29 July 2026

PIM - Protocol Independent Multicast (IPv4)RIP - Routing Information Protocol