IGMP querier

[ShKhan]

Dear All,

Can I point all switches to one querier in the l2 multicast network? Attached is the sample topology with each device config pointing to one switch NXOS1, which is the querier, or other devices will discover the querier NSOX1 via IGMP snooping ?

And if I have more than one Multicast source (NXOS1 and NXOS2), can I make both querier for the sources attached to them ?

Please advise!

Regards

[Jon Marshall]

You shouldn't need to configure the querier on every switch, you just need it on one of the switches. 

The querier is there simply to make IGMP queries within the vlan so that all switches running IGMP snooping can listen to the IGMP responses and update their mac address tables accordingly. 

You only need the querier function if you are not routing multicast traffic so you have not enabled PIM on a L3 interface because PIM would then be responsible for the IGMP queries. 

Jon

[ShKhan]

from Juniper:

Using the Device as an IGMP Querier

"If you configure multiple devices to be IGMP queriers, the device with the lowest (smallest) IGMP querier source address takes precedence and acts as the querier. The devices with higher IGMP querier source addresses stop sending IGMP queries unless they do not receive IGMP queries for 255 seconds. If the device with a higher IGMP querier source address does not receive any IGMP queries during that period, it starts sending queries again."

The same can be achieved in Cisco?

[ShKhan]

IGMP Snooping information for vlan 10
IGMP snooping enabled
Lookup mode: IP
Optimised Multicast Flood (OMF) enabled
IGMP querier present, address: 10.10.10.252, version: 3, i/f Eth1/2
Querier interval: 125 secs
Querier last member query interval: 25 secs
Querier robustness: 2
Switch-querier enabled, address 10.10.10.253, currently not running
IGMPv3 Explicit tracking enabled
IGMPv2 Fast leave enabled
IGMPv1/v2 Report suppression enabled
IGMPv3 Report suppression disabled
Link Local Groups suppression enabled
Router port detection using PIM Hellos, IGMP Queries
Number of router-ports: 2
NXOS2#

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

IGMP Snooping information for vlan 10
IGMP snooping enabled
Lookup mode: IP
Optimised Multicast Flood (OMF) enabled
IGMP querier present, address: 10.10.10.252, version: 3
Querier interval: 125 secs
Querier last member query interval: 25 secs
Querier robustness: 2
Switch-querier enabled, address 10.10.10.252, currently running
IGMPv3 Explicit tracking enabled
IGMPv2 Fast leave enabled
IGMPv1/v2 Report suppression enabled
IGMPv3 Report suppression disabled
Link Local Groups suppression enabled
Router port detection using PIM Hellos, IGMP Queries
Number of router-ports: 2
NXOS1#

[Jon Marshall · Accepted solution]

Yes it can and the lowest IP becomes the querier as far as I know. 

Jon

[ShKhan]

Thank you very much !