IGMP Configuration Problems

[ppearson1]

Hello,

We are looking to implement IGMP Multicast for a singular VLAN but seem to be missing something..
The current setup is we have a layer 3 switch with an SVI and a layer 2 switch connected with multicast clients connected. At current, IGMP snooping looks to be working on the correct vlan

Vlan 100:
--------
IGMP snooping : Enabled
Pim Snooping : Disabled
IGMPv2 immediate leave : Enabled
Explicit host tracking : Enabled
Multicast router learning mode : pim-dvmrp
CGMP interoperability mode : IGMP_ONLY
Robustness variable : 2
Last member query count : 2
Last member query interval : 1000

----------------------------------

Vlan100 is up, line protocol is up
Internet address is 10.90.100.1/23
IGMP is disabled on interface
Multicast routing is disabled on interface
Multicast TTL threshold is 0
No multicast groups joined by this system

----------------------------------------

IGMP Connected Group Membership
Group Address Interface Uptime Expires Last Reporter Group Accounted

------------------------------------------
ip igmp snooping querier
ip igmp snooping vlan 100 querier address 10.90.100.1

On the Layer 2 switch, we are receiving the below debug errors:

% Illegal group address 10.90.100.1

Jun 13 08:28:26 BST: IGMPQR: vlan_id 100: GQ with src addr 10.90.100.1 received on port Po100 in Disabled state

Any help at all would be appreciated!

Cheers

[marce1000]

  - Based on the information provided, it seems that IGMP snooping is enabled on the Layer 3 switch for VLAN 100, but IGMP is disabled on the interface facing the Layer 2 switch. This is likely the cause of the issue you are experiencing. To resolve this, you need to enable IGMP on the Layer 3 switch interface that connects to the Layer 2 switch. Here's how you can do it: Access the Layer 3 switch's configuration mode. Locate the interface that connects to the Layer 2 switch. In this case, it appears to be VLAN 100 with the IP address 10.90.100.1/23.

Enable IGMP on the interface using the following command:
         interface vlan 100
          ip igmp enable

After enabling IGMP on the Layer 3 switch interface, the Layer 2 switch should be able to receive IGMP group membership information without generating the "Illegal group address" error. Make sure that both switches are properly configured for IGMP snooping to allow multicast traffic to flow correctly.
It's also worth mentioning that you have PIM snooping disabled on the Layer 3 switch. If you intend to use PIM for multicast routing, you'll need to enable PIM snooping on the appropriate VLAN interfaces. However, if you only require IGMP snooping for VLAN 100, PIM snooping may not be necessary in this case.

 M.

[ppearson1]

Hi Marce,

Many thanks for your input! Unfortunatly, that command is not available on the interface:

(config-if)#ip igmp ?
access-group IGMP group access group
explicit-tracking Enable/Disable IGMP explicit-tracking
helper-address IGMP helper address
immediate-leave Leave groups immediately without sending last member query, use for one host network only
join-group IGMP join multicast group
last-member-query-count IGMP last member query count
last-member-query-interval IGMP last member query interval
limit IGMP limit
mroute-proxy Mroute to IGMP proxy
proxy-service Enable IGMP mroute proxy service
querier-timeout IGMP previous querier timeout
query-interval IGMP host query interval
query-max-response-time IGMP max query response value
static-group IGMP static multicast group
tcn IGMP TCN configuration
unidirectional-link IGMP unidirectional link multicast routing
v3-query-max-response-time IGMP v3 max query response value
v3lite Enable/disable IGMPv3 Lite
version IGMP version

Switch model is: C9500-40X running code 16.8.1a 

Kind Regards,

[Giuseppe Larosa]

Hello @ppearson1 ,

enable

ip multicast routing

int vlan 100

ip pim sparse-dense mode

When enabling PIM on an interface also IGMP is enabled

at this point you don't need to configure an IGMP snooping querier on the L2 switch the L3 switch will do this job on the VLAN.

Hope to help

Giuseppe

[rasmus.elmholt]

Hi,

To me it seems like you are trying to configure the L3 switches address as the source on the L2 switch. The querier address you configure with ip igmp snooping vlan 100 querier address needs to be an address on the local switch.

Take a look at this description of the querier feature: 

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus3548/sw/92x/configuration/guide/b-cisco-nx-os-3548-layer-2-switching-configuration-guide-92x/b-cisco-nx-os-3548-layer-2-switching-configuration-guide-92x_chapter_01100.pdf

Example configuration can be found here: 

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst_microswitches/software/releases/15_2_8_e/configuration_guide/ip_multicast/b_1528e_ip_mcast_snooping_cms_cg/configuing_igmp_snooping.html#task_r24_dsc_yjb

IGMP Snooping Querier
When there is no multicast router in the VLAN to originate the queries, you must configure an IGMPsnooping
querier to send membership queries.
When an IGMP snooping querier is enabled, it sends out periodic IGMP queries that trigger IGMP report
messages from hosts that want to receive IP multicast traffic. IGMP snooping listens to these IGMP reports
to establish appropriate forwarding.
Currently, you can configure the same SVI IP address for the switch querier and the IGMP snooping querier.
Both queriers will then be active at the same time, and both queriers will send general queries to the VLAN
periodically. To prevent thisfrom happening, ensure that you use different IPaddressesfor the IGMPsnooping
querier and the switch querier.