How to get the packet per second rate of a multicast group stream in the output of the 'show multicast route extensive' command on EX-series switches

Description

This article provides information on how to get the multicast forwarding counters from the packet forwarding engine (PFE).

Symptoms

At times, for troubleshooting multicast issues, we need to know the multicast traffic forwarding rate for a specific multicast group. But the EX switch does not display the correct multicast-forwarding counters in the output of the show multicast route extensive command.

In the following example, the EX-SW-RP (EX4200) switch is configured as RP for the 226.1.1.38 group. The Multicast source for the 226.1.1.38 group is connected to the switch (EX-SW-Src) and the Multicast client for the same group is connected to the switch (EX-SW-GW).

(MC-Source_226.1.1.38)-------[EX-SW-Src]-----[EX-SW-RP]----[EX-SW-GW]-------(MC-Client_226.1.1.38)

Here, the EX-SW-RP switch is not showing the multicast forwarding counters correctly in the output of the show multicast route extensive command for the 226.1.1.18 group:

root@EX_SW_RP> show multicast route group 226.1.1.38 extensive Family: INET Group: 226.1.1.38 Source: 10.10.200.11/32 Upstream interface: vlan.200 Downstream interface list: vlan.900 Session description: Unknown Statistics: 0 kBps, 0 pps, 10764 packets <<<<<<<<<<<<<<<< here for this multicast route group 0 pps Next-hop ID: 131071 Upstream protocol: PIM Route state: Active Forwarding state: Forwarding Cache lifetime/timeout: 360 seconds Wrong incoming interface notifications: 0

Solution

Due to hardware design, we cannot get the packet per second value for any specific multicast group stream (multicast forwarding counters) from the show multicast route extensive command.

As a workaround, the request multicast route counter group <gip> source <sip> command has been introduced to resolve the multicast counter issue.

Here is the procedure to get the value of multicast forwarding counters for a specific multicast group (in this example, the group is 224.1.1.38 and source is 10.10.200.11 ):

Run the following command to enable the multicast forwarding counters for the group:

root@EX-SW-RP> request multicast route counter group 226.1.1.38 source 10.10.200.11

Verify if the switch is showing the correct multicast forwarding counter for the group:

root@EX-SW-RP> show multicast route group 226.1.1.38 extensive
Family: INET

Group: 226.1.1.38
Source: 10.10.200.11/32
Upstream interface: vlan.200
Downstream interface list:
vlan.900
Session description: Unknown
Statistics: 0 kBps, 477 pps, 8442 packets < started to show the correct packet per second rate of multicast stream
Next-hop ID: 131071
Upstream protocol: PIM
Route state: Active
Forwarding state: Forwarding
Cache lifetime/timeout: 360 seconds
Wrong incoming interface notifications: 0

Note :

The packets per second (pps) output is not always a true value of the actual packet/seconds value of the multicast forwarding counter.
In case of the EX-4200 Virtual Chassis, the output of 'show multicast route extensive' command may show the pps rate as multiple times of the actual pps rate of the multicast stream. In that case, the displayed packets-per-seconds (pps) rate is number of FPC's times the actual multicast stream traffic rate.