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New Member

multicast output drops

I have a SVI running PIM. With 1 sender and 1 receiver on a single muticast group over a the same VLAN, I get no data loss. As soon as I add another receiver (igmp join), I experience data loss and output drops on the all of the receivers ports.

Hall of Fame Super Silver

Re: multicast output drops

Hello Philip,

may you add some more details like:


IOS image

config of your SVI

sh ip igmp groups

sh ip igmp snooping vlan SVI#

sh ip igmp snooping groups

sh ip igmp snooping querier

this can help to understand what is happening.

Hope to help


New Member

Re: multicast output drops

Oct 13 14:45:46.260 EDT: %SYS-5-CONFIG_I: Configured from console by chief on vty0 ( ver

Cisco IOS Software, Catalyst 4000 L3 Switch Software (cat4000-I9S-M), Version 12.2(25)EWA4, RELEASE SOFTWARE (fc1)

Technical Support:

Copyright (c) 1986-2005 by Cisco Systems, Inc.

Compiled Fri 23-Sep-05 13:31 by ssearch

Image text-base: 0x10000000, data-base: 0x114DFF08

ROM: 12.2(20r)EW1

Dagobah Revision 226, Swamp Revision 34

njds04 uptime is 2 years, 48 weeks, 3 days, 22 hours, 31 minutes

System returned to ROM by power-on

System restarted at 15:59:47 est Wed Nov 8 2006

System image file is "bootflash:"

cisco WS-C4506 (MPC8245) processor (revision 10) with 262144K bytes of memory.

Processor board ID FOX072301Q9

MPC8245 CPU at 266Mhz, Supervisor II+

Last reset from PowerUp

5 Virtual Ethernet interfaces

242 Gigabit Ethernet interfaces

511K bytes of non-volatile configuration memory.

Configuration register is 0x2101




interface GigabitEthernet2/1

description *** TRUNK to njds03_g2/1 ***

switchport trunk encapsulation isl

switchport trunk allowed vlan 200-203

switchport mode trunk

logging event link-status

speed 1000

duplex full


interface Vlan200

ip address

ip helper-address

ip helper-address

ip helper-address

ip helper-address

ip directed-broadcast

ip pim sparse-dense-mode

standby 200 ip

standby 200 priority 110

standby 200 preempt

standby 200 name PROD_FLEX


njds04#sh ip igmp groups

IGMP Connected Group Membership

Group Address Interface Uptime Expires Last Reporter Vlan200 15:00:02 00:02:40 Vlan200 05:41:13 00:02:43 Vlan200 14:46:35 00:02:38 Vlan200 14:46:29 00:02:47 Vlan200 15:00:01 00:02:39 Vlan200 15:00:01 00:02:38 Vlan200 10:32:46 00:02:41 Vlan200 10:22:09 00:02:38 Vlan200 15:00:02 00:02:43

njds04#sh ip igmp snooping vlan 200

Global IGMP Snooping configuration:


IGMP snooping : Enabled

IGMPv3 snooping : Enabled

Report suppression : Enabled

TCN solicit query : Disabled

TCN flood query count : 2

Vlan 200:


IGMP snooping : Enabled

IGMPv2 immediate leave : Disabled

Explicit host tracking : Enabled

Multicast router learning mode : pim-dvmrp

CGMP interoperability mode : IGMP_ONLY

njds04#sh ip igmp snooping groups

Vlan Group Version Port List


200 v2 Gi2/1

200 v2 Gi5/2, Gi5/6

200 v2 Gi5/5

200 v2 Gi2/24, Gi2/26, Gi5/2, Gi5/5, Gi5/6

200 v2 Gi2/1, Gi5/5

200 v2 Gi5/2, Gi5/6

200 v2 Gi2/1, Gi2/24, Gi2/26, Gi5/2, Gi5/5, Gi5/6

200 v2 Gi2/1

200 Gi2/1

njds04#sh ip igmp snooping querier

Vlan IP Address IGMP Version Port


200 v2 Gi2/1

Hall of Fame Super Silver

Re: multicast output drops

Hello Philip,

sorry for the late answer

I don't see anything wrong in the shows you have provided.

I tried to do a bug search for your switch and IOS image

the search of bugs related to multicast provides 170 entries.

Hope to help


New Member

Re: multicast output drops

If the switch is running the following modules:


and if there are 2 receiver hosts on the same ASIC(I am assuming ports 1-8) would there be an issue if the sender was sending multicast at nearly gigbit speed (on a different blade), would the switch drop data since it would be bound by the 1 gigabit shared between the 8 ports on the receiver's ASIC

Hall of Fame Super Silver

Re: multicast output drops

Hello Philip,

you have hit the ball!

this limitation exists in this linecard and we have seen it with unicast traffic.

I cannot find the document now, but I've seen the same with unicast traffic in our network during new servers testings.

1 Gbps multicast traffic ? are you using a traffic generator?

Hope to help


New Member

Re: multicast output drops

Yes I am using atraffic generator - mtools it is able to generate linespeed traffic @ the sender