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cmcast-joins-limit-inet (MVPN Selective Tunnels)


Hierarchy Level


Configure the maximum number of IPv4 customer multicast entries

The purpose of the cmcast-joins-limit-inet statement is to supplement the multicast forwarding-cache limit when the MVPN rpt-spt mode is configured and when traffic is flowing through selective service provider multicast service inteface (S-PMSI) tunnels and is forwarded by way of the (*,G) entry, even though the forwarding cache limit has already blocked the forwarding entries from being created.

The cmcast-joins-limit-inet statement limits the number of Type-6 and Type-7 routes. These routes contain customer-route control information.

You can configure the cmcast-joins-limit-inet statement only when the MVPN mode is rpt-spt.

This statement is independent of the leaf-tunnel-limit-inet statement and of the forwarding-cache threshold statement.

The cmcast-joins-limit-inet statement is applicable on the egress PE router. It limits the customer multiccast entries created in response to PIM (*,G) and (S,G) join messages. This statement is applicable to both type-6 and type-7 routes because the intention is to limit the egress forwarding entries, and in rpt-spt mode, an MVPN creates forwarding entries for both of these route types (in other words, for both (*,G) and (S,G) entries). However, this statement does not block BGP-created customer multicast entries because the purpose of this statement is to prevent the creation of forwarding entries on the egress PE router only and only for non-remote receivers. If remote-side customer multicast entries or forwarding entries need to be limited, you can use forwarding-cache threshold on the ingress routers, in which case this statement is not required.

By placing a limit on the customer multicast entries, you can ensure that when the limit is reached or the maximum forwarding state is created, all further local join messages will be blocked by the egress PE router. This ensures that traffic is flowing for only those multicast entries that are permitted.

If another PE router is interested in the traffic, it might pull the traffic from the ingress PE router by sending type-6 and type-7 routes. To prevent forwarding in this case, you can configure the leaf tunnel limit (leaf-tunnel-limit-inet). By preventing type-4 routes from being sent in response to type-3 routes, the formation of selective tunnels is blocked when the tunnel limit is reached. This ensures that traffic flows only for the routes within the tunnel limit . For all other routes, traffic flows only to the PE routers that have not reached the configured limit.

Setting the cmcast-joins-limit-inet statement or reducing the value of the limit does not alter or delete the already existing and installed routes. If needed, you can run the clear pim join command to force the limit to take effect. Those routes that cannot be processed because of the limit are added to a queue, and this queue is processed when the limit is removed or increased and when existing routes are deleted.





Maximum number of customer multicast entries for IPv4.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 13.3.