Configuring Multicast Load Splitting
Context
By default, if there are multiple equal-cost routes to a multicast source, a switch applies the following route selection rules during a reverse path forwarding (RPF) check:
- If the equal-cost routes are in the same routing table, for example, a unicast routing table, multicast static routing table, or Multiprotocol Border Gateway Protocol (MBGP) routing table, the switch selects the route with the largest next-hop address as the RPF route.
- If the equal-cost routes are in different routing tables, the switch selects the route with the highest preference. If multiple routes have the highest preference, the switch selects the route with the longest mask length. If multiple routes have the longest preference, the switch uses an algorithm to select an RPF route.
In this default configuration, the switch selects only one route as the RPF route, regardless of which condition is met. Multicast load splitting enables the switch to distribute multicast data among multiple equal-cost paths based on a specific load splitting policy. This function improves quality of multicast forwarding.
It is recommended that you use a fixed load splitting policy that best suits your network. The stable-preferred or balance-preferred load splitting policy is recommended.
The load splitting timer and load splitting weights can be configured when the stable-preferred or balance-preferred load splitting policy is used.
If Protocol Independent Multicast - Dense Mode (PIM-DM) is enabled on the current switch, the stable-preferred or balance-preferred policy cannot be used.
Procedure
- Run system-view
The system view is displayed.
- Run multicast load-splitting { balance-preferred | stable-preferred | source | group | source-group }
Multicast load splitting is configured.
The keywords in the command specify different multicast load splitting policies:
balance-preferred: ensures even load distribution among forwarding paths. Use this policy in scenarios where users frequently join and leave multicast groups. It enables traffic distribution to automatically adapt to frequent changes in group memberships.
If this load splitting policy is used, the switch automatically adjusts traffic on equal-cost routes when equal-cost routes are added or deleted, multicast routing entries are deleted, or load splitting weights on interfaces are changed.
stable-preferred: ensures stable multicast forwarding. Use this policy on a network with stable multicast services.
If this load splitting policy is used, the switch automatically adjusts traffic on equal-cost routes when equal-cost routes are added or deleted. However, when multicast routing entries are deleted or load splitting weights on interfaces are changed, the switch does not automatically adjust the traffic on the equal-cost routes.
group: load splitting by group address. Use this policy in scenarios where one multicast source sends data to multiple groups.
source: load splitting by source address. Use this policy in scenarios where one group receives data from multiple sources.
source-group: load splitting by source address and group address. Use this policy in scenarios where multiple sources send data to multiple groups.
- (Optional) Run multicast load-splitting-timer interval
The multicast load splitting timer is set.
By default, the value of a load splitting timer is 1800 seconds.
- (Optional) Set the load splitting weight
of an interface.
- (Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.
By default, an Ethernet interface works in Layer 2 mode.
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
- (Optional) On an Ethernet interface, run undo portswitch