IGMP Snooping Querier Address

[Nik Noltenius]

Hi everyone,

I'm kind of stealing a question from another discussion, but I'm afraid it won't be answered there since the original discussion is already marked as answered.

So as CK_COO in

https://community.cisco.com/t5/application-centric/l2-igmp-query-on-aci-leaf-switches/td-p/3056026

I would also very much like to know what's so special about the IGMP Querier address under the bridge domain. 

Can I simply check the box for IGMP querier at the subnet I've defined for the Bridge Domain or do I really have to add a unique IP?

Unfortunately the guide is not that clear an lacking a real example (https://www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/2-x/L3_config/b_Cisco_APIC_Layer_3_Configuration_Guide/b_Cisco_APIC_Layer_3_Configuration_Guide_chapter_010000.html#concept_3B3D0956578C40EA91AA7A01487CE62B%C2%A0).

Kind regards,

Nik

[Manuel Velasco · Accepted solution]

Hi Nik,

In order to have an IGMP querier on your BD you must enable the querier under the BD as well as under the subnet; which will act as the querier.  If you just do it on the subnet, this will not be enough to push the configuration.  You don't have to add a unique ID, the subnet SVI IP will be use as the querier.

You can validate this by running the following command

show ip igmp snooping vlan #  

where # represents the PI vlan ID of your BD.

If you want to find what this value is, you can simply run the following command

show vlan extended | grep  <BD-NAME> 

See Example below:

fab4-p1-leaf1# show vlan extended | grep MV-BD
 19   MV-Lab:MV-BD                     active    Eth1/29, Eth1/30, Eth1/33, Po1

fab4-p1-leaf1# show ip igmp snooping vlan 19
IGMP Snooping information for vlan 19
  IGMP snooping enabled
  Lookup mode: IP
  Optimised Multicast Flood (OMF) disabled
  IGMP querier present, address: 192.168.1.1, version: 3
  Querier interval: 125 secs
  Querier last member query interval: 1 secs
  Querier robustness: 2
  Switch-querier enabled, address 192.168.1.1/24, currently running
  IGMPv3 Explicit tracking enabled
  IGMPv2 Fast leave disabled
  IGMPv1/v2 Report suppression enabled
  IGMPv3 Report suppression enabled
  Link Local Groups suppression enabled
  Router port detection using PIM Hellos, IGMP Queries
  Number of router-ports: 0
  Number of groups: 2
  VLAN vPC function enabled
  Multicast Routing disabled on VLAN
  Active ports:
    Eth1/29     Eth1/30     Eth1/33     Po1

I hope this helps

[Nik Noltenius]

Thank you, Manuel! That helps a lot.

[b.michel]

Hello,

is it in addition supported to use the same Querier IP Address in several BDs with Unicast Routing disabled? In this case I would be able to configure the same IP Address in all Firewall protected BDs without any knowledge which Endhost IP Adresses are used in that BD. Fore example the hosts use 10.1.1.0/24 in BD1, 10.2.2.0/24 in BD2 and both BDs use the same Querier IP 192.168.10.10 (BD Unicast Routing disabled).

Kind regards

Bodo