4.11 Multicast Policy
| Field |
Value |
| Document ID |
SDWAN-POL-4.11 |
| Version |
1.0 |
| Last Updated |
December 2025 |
| Author |
Network Architecture Team |
| Classification |
Internal Use |
1. Executive Summary
Multicast over SD-WAN enables efficient one-to-many traffic distribution for applications like video streaming, software updates, and real-time communications. This section defines Abhavtech's multicast policy design including PIM, IGMP, and overlay multicast replication.
1.1 Multicast Architecture Overview
+------------------------------------------------------------------+
| MULTICAST OVER SD-WAN |
+------------------------------------------------------------------+
| |
| Traditional Multicast Issues: |
| - MPLS required PIM/IGMP on provider network |
| - Complex configuration per site |
| - Limited scalability |
| |
| SD-WAN Multicast Solution: |
| +----------------------------------------------------------+ |
| | Source --> Hub WAN Edge --> Replication --> Branch | |
| | Point | |
| | | |
| | Methods: | |
| | 1. Headend Replication (at source) | |
| | 2. Replicator (centralized) | |
| | 3. PIM/Auto-RP (native multicast) | |
| +----------------------------------------------------------+ |
| |
+------------------------------------------------------------------+
2. Multicast Methods in SD-WAN
2.1 Multicast Replication Options
| Method |
Description |
Use Case |
Scalability |
| Headend Replication |
Source WAN Edge replicates |
Small deployments |
Low (CPU intensive) |
| SD-WAN Replicator |
Dedicated replicator device |
Medium deployments |
Medium |
| PIM/Auto-RP |
Native multicast routing |
Large deployments |
High |
2.2 Abhavtech Multicast Strategy
| Application |
Method |
Location |
| Video Streaming |
PIM/Auto-RP |
Hub sites |
| Software Updates |
Headend Replication |
DC |
| Real-time Events |
SD-WAN Replicator |
Mumbai Hub |
| Voice Conferencing |
Unicast (for reliability) |
N/A |
3. PIM Configuration
3.1 PIM Sparse Mode
! Enable PIM Sparse Mode on WAN Edge
ip multicast-routing distributed
!
! Service VPN interface configuration
interface GigabitEthernet0/0/2
description LAN-Employee
ip address 172.16.1.1 255.255.255.252
ip pim sparse-mode
!
! Tunnel interface configuration
interface Tunnel100
ip pim sparse-mode
!
! RP configuration
ip pim rp-address 10.10.1.10 ! Mumbai DC as RP
3.2 PIM Auto-RP Configuration
! Configure Auto-RP for dynamic RP discovery
! Mumbai Hub as RP
ip pim autorp listener
ip pim send-rp-announce Loopback0 scope 16
ip pim send-rp-discovery Loopback0 scope 16
!
! Branch sites as Auto-RP listeners
ip pim autorp listener
3.3 PIM Timers
! Optimize PIM timers for WAN
ip pim spt-threshold infinity ! Stay on shared tree
ip pim query-interval 30
ip pim neighbor-filter PIM-NEIGHBOR-ACL
!
access-list PIM-NEIGHBOR-ACL permit 10.0.0.0 0.255.255.255
4. IGMP Configuration
4.1 IGMP Snooping
! Enable IGMP snooping on LAN interfaces
ip igmp snooping
ip igmp snooping vlan 10
!
! IGMP version
interface GigabitEthernet0/0/2
ip igmp version 3
ip igmp query-interval 60
ip igmp query-max-response-time 10
4.2 IGMP Proxy
! IGMP proxy for branch sites without full PIM
ip igmp proxy
!
interface GigabitEthernet0/0/2
ip igmp proxy-service
!
interface Tunnel100
ip igmp mroute-proxy Loopback0
5. Headend Replication
5.1 Headend Replication Configuration
! Enable headend replication in SD-WAN Manager
! Configuration > Templates > Feature Template > Multicast
!
! CLI equivalent:
omp
advertise connected
advertise static
advertise bgp
advertise ospf
!
multicast
headend-replication
source
group-range 239.0.0.0/8
!
!
5.2 Headend Replication Topology
+------------------------------------------------------------------+
| HEADEND REPLICATION TOPOLOGY |
+------------------------------------------------------------------+
| |
| Multicast Source |
| | |
| v |
| +----------+ |
| | Mumbai | Replicates to each branch |
| | WAN Edge |--+---> Bangalore WAN Edge |
| | (Source) | |---> Delhi WAN Edge |
| +----------+ |---> Noida WAN Edge |
| +---> London WAN Edge |
| +---> Frankfurt WAN Edge |
| |
| CPU: Linear increase with receivers |
| BW: N x stream size (source upload) |
+------------------------------------------------------------------+
6. SD-WAN Replicator
6.1 Replicator Configuration
! Designate Mumbai Hub as replicator
! SD-WAN Manager: Configuration > Devices > Multicast Replicator
!
! CLI on replicator device:
omp
multicast
replicator
vpn 10
ip group-range 239.0.0.0/8
ip source 10.10.100.0/24
!
!
!
6.2 Replicator Topology
+------------------------------------------------------------------+
| SD-WAN REPLICATOR TOPOLOGY |
+------------------------------------------------------------------+
| |
| Multicast Source |
| | |
| v |
| +----------+ +------------+ |
| | Source |------->| Replicator |--+---> Branch 1 |
| | Site | | (Mumbai) | |---> Branch 2 |
| +----------+ +------------+ |---> Branch 3 |
| +---> Branch N |
| |
| Offloads replication from source |
| More scalable than headend replication |
+------------------------------------------------------------------+
7. Multicast Groups Configuration
7.1 Group Ranges
| Group Range |
Application |
VPN |
Method |
| 239.1.0.0/24 |
Video streaming |
10 |
PIM |
| 239.2.0.0/24 |
Software updates |
10 |
Headend |
| 239.3.0.0/24 |
Real-time events |
10 |
Replicator |
| 239.10.0.0/24 |
Voice (backup) |
40 |
PIM |
7.2 Group Access Control
! Restrict multicast group membership
ip access-list extended MULTICAST-GROUPS-ALLOWED
permit ip any 239.1.0.0 0.0.255.255
permit ip any 239.2.0.0 0.0.255.255
permit ip any 239.3.0.0 0.0.255.255
deny ip any 224.0.0.0 15.255.255.255
!
interface GigabitEthernet0/0/2
ip igmp access-group MULTICAST-GROUPS-ALLOWED
8. Per-VPN Multicast
8.1 VPN 10 - Employee Multicast
! Full multicast support for employee VPN
omp
multicast
vpn 10
pim-mode sparse
rp-address 10.10.1.10
!
group-range 239.0.0.0/8
!
!
!
8.2 VPN 40 - Voice Multicast
! Limited multicast for voice (conference announcements)
omp
multicast
vpn 40
pim-mode sparse
rp-address 10.19.1.10
!
group-range 239.10.0.0/24 ! Limited range
!
!
!
8.3 VPN 20/30/100 - No Multicast
! Guest, IoT, and PCI VPNs do not support multicast
! Multicast traffic is dropped by default
9. Multicast QoS
9.1 Multicast Traffic Classification
! Classify multicast traffic for QoS
class-map match-any MULTICAST-VIDEO
match dscp af41
match access-group name MULTICAST-VIDEO-ACL
!
ip access-list extended MULTICAST-VIDEO-ACL
permit ip any 239.1.0.0 0.0.255.255
!
policy-map WAN-QOS
class MULTICAST-VIDEO
priority percent 20
set dscp af41
9.2 Multicast Bandwidth Control
! Limit multicast bandwidth per interface
interface GigabitEthernet0/0/0
rate-limit output access-group MULTICAST-ACL 50000000 9375000 18750000
conform-action transmit
exceed-action drop
!
ip access-list extended MULTICAST-ACL
permit ip any 224.0.0.0 15.255.255.255
10. Monitoring and Verification
10.1 Verification Commands
! Check multicast routing
show ip mroute
show ip mroute summary
show ip mroute count
! Check PIM neighbors
show ip pim neighbor
show ip pim interface
! Check IGMP groups
show ip igmp groups
show ip igmp membership
! Check OMP multicast
show sdwan omp multicast-routes
show sdwan omp multicast-auto-discover
! Check replicator status
show sdwan replicator
! Sample output:
! MULTICAST GROUP SOURCE OUTGOING INTERFACES
! 239.1.1.1 10.10.100.10 Tunnel100, Tunnel200
! 239.2.1.1 10.10.100.20 Tunnel100
10.2 Multicast Metrics
| Metric |
Threshold |
Action |
| PIM Neighbor Count |
Expected value |
Investigate if low |
| IGMP Groups |
Expected range |
Check for storms |
| Replication Load |
<80% CPU |
Scale if exceeded |
| Multicast Drops |
>1% |
Investigate QoS |
11. Troubleshooting
11.1 Common Issues
| Issue |
Symptom |
Resolution |
| No multicast traffic |
Receivers don't get stream |
Check PIM/IGMP |
| High CPU on source |
Headend overload |
Use replicator |
| Multicast storm |
Network saturation |
Check TTL, RP config |
| Cross-VPN leak |
Wrong VPN receives |
Verify VPN isolation |
11.2 Debug Commands
! Debug multicast (use with caution)
debug ip mrouting
debug ip pim
debug ip igmp
! Debug OMP multicast
debug sdwan omp multicast
12. Best Practices
12.1 Multicast Guidelines
| Guideline |
Recommendation |
| Use PIM Sparse |
For all deployments |
| Limit Group Ranges |
Prevent unauthorized multicast |
| QoS for Multicast |
Prioritize video streams |
| Monitor Replication |
Track CPU and bandwidth |
| Test Before Production |
Validate in lab |
12.2 Scalability Recommendations
| Deployment Size |
Recommended Method |
| <50 sites |
Headend replication |
| 50-200 sites |
SD-WAN replicator |
| >200 sites |
PIM/Auto-RP |
13. Summary
| Element |
Abhavtech Configuration |
| Primary Method |
PIM/Auto-RP |
| RP Location |
Mumbai DC (10.10.1.10) |
| Replicator |
Mumbai Hub (backup) |
| Multicast VPNs |
VPN 10 (Employee), VPN 40 (Voice) |
| Group Ranges |
239.x.x.x (enterprise) |
| QoS |
AF41 for video multicast |
Document Version: 1.0
Last Updated: December 2025
Next Review: March 2026