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New Member

3750x multicast problem

Hi all,

i have a problem with multicast flooding in our network.

We have two stacks of 3750x switches, on each stack connected Video servers (that get real video streams from IP cameras), each server has a number of IP cameras .This traffic is unicast.

We also have a viewing station that get the video from Video servers by multicast (PIM SM). Each IP cameras stream is a multicast group .

Viewing station and Video servers separated by vlans.L3 of Vdeo servers and viewing station and the RP is the 3750x switch himself.

My problem is:

1. I see that all multicast traffic is flooded throught all Video servers vlan (each time that vieing station wants to join to newIGMP group) whenever most of      servers not have those groups. Even if i connect my laptop to Video servers vlan i can see the multicast traffic . i have igmp snooping enable on all vlan       interfaces

2. The CPU of 3750X most of time on 50% with peaks of 80-90%

3. First time opening video (join to new new m.route) on vieng station is always corrupted for 1-2 sec and after it its works fine

my topology:

IP cameras-->PON network-->Aggregation switches (4948)--10G-->ASA5585-ssm20--10G-->Video_Swithes_3750X--->Video_servers(vlan x)

                                                                                                                                                                     |--->Veiwng_stations(vlan y)

i cant find solution for that for a long time, i thought to move to PIM DM ? moving to to bidir-pim -  not help, still have a flooding.



Everyone's tags (3)
VIP Super Bronze

3750x multicast problem


You can try blocking Multicast on the interfaces you don't want to see Multicast. 

here is the command:

Under the physical interfaces:

switchport block multicast

than test again.


New Member

3750x multicast problem


"Switchport block multicast" blocks unknown multicast forwarding to the port.


Only  pure Layer 2 multicast traffic is blocked. Multicast packets that  contain IPv4 or IPv6 information in the header are not blocked.

3750x multicast problem

Which IGMP version are you using?


New Member

3750x multicast problem

its IGMPv2

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