Troubleshooting Tip: FortiGate interface changes its state from IGMP Querier to Non-Querier

[aneshcheret]

Description
This article describes how to fix the issue when a FortiGate interface changes its state from IGMP Querier to Non-Querier.

Solution
On a FortiGate, an IGMP state change from Querier to Non-Querier which leads to the Multicast service interruption.
When a Fortigate interface IGMP state changes to Non-Querier, it means that there is some other device in the network, which is acting as Querier.
This can be seen in multi-vendor network architecture containing Cisco, Huawei, HP, Avaya, Dell devices as every device has different IGMP query interval.

IGMP STATUS WHEN MULTICAST IS WORKING:

# get router info multicast igmp interface
Interface port2 (Index 12)
IGMP Enabled, Active, Querier, Configured for version 2           <------------------ FortiGate port2 is acting as IGMP querier
Internet address is 192.168.16.1

IGMP STATUS WHEN MULTICAST IS NOT WORKING:

# get router info multicast igmp interface
Interface port2 (Index 12)
IGMP Enabled, Active, Non-Querier, Configured for version 2       <------------------------- FortiGate port2 is acting as IGMP Non-Querier
Internet address is 192.168.16.1
IGMP querying router is X.X.X.X   

DEBUG OUTPUT LOGS:

# diagnose ip router igmp all enable
# diagnose ip router igmp level info
# diagnose debug enable
2019-07-26 08:08:21 id=20301 logdesc="Routing log" msg="NSM: [IGMP-DECODE] Dec Msg: IGMP Membership Query, Max. Rsp. Code 100"
2019-07-26 08:08:21 id=20301 logdesc="Routing log" msg="NSM: [IGMP-DECODE] Dec Query: Lower IP 0.0.0.0 on port2"
2019-07-26 08:08:21 id=20301 logdesc="Routing log" msg="NSM: [IGMP-DECODE] Dec Query: Ouerier->Non-querier on port2"

To fix this problem, reduce the IGMP query-interval and query-timeout making it lower than any other device in the network is using the following commands:

# config router multicast
    config interface
        edit "port2"
            config igmp
                set query-interval 20 >>> Set value less than other device IGMP Query interval
                set query-timeout 60  >>> Set value less than other device IGMP Query timeout
            end
        next
    end
end